diff --git a/src/driver_amiplus.cc b/src/driver_amiplus.cc
index b1c17e6..9a17db6 100644
--- a/src/driver_amiplus.cc
+++ b/src/driver_amiplus.cc
@@ -53,7 +53,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         NoDifVifKey,
@@ -68,7 +68,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(total_energy_consumption_kwh_, Unit::KWH),
         GET_FUNC(total_energy_consumption_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "current_power_consumption",
         Quantity::Power,
         NoDifVifKey,
@@ -83,7 +83,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(current_power_consumption_kw_, Unit::KW),
         GET_FUNC(current_power_consumption_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_production",
         Quantity::Energy,
         DifVifKey("0E833C"),
@@ -98,7 +98,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(total_energy_production_kwh_, Unit::KWH),
         GET_FUNC(total_energy_production_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "current_power_production",
         Quantity::Power,
         DifVifKey("0BAB3C"),
@@ -113,7 +113,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(current_power_production_kw_, Unit::KW),
         GET_FUNC(current_power_production_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "voltage_at_phase_1",
         Quantity::Voltage,
         DifVifKey("0AFDC9FC01"),
@@ -128,7 +128,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(phase_1_v_, Unit::Volt),
         GET_FUNC(phase_1_v_, Unit::Volt));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "voltage_at_phase_2",
         Quantity::Voltage,
         DifVifKey("0AFDC9FC02"),
@@ -143,7 +143,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(phase_2_v_, Unit::Volt),
         GET_FUNC(phase_2_v_, Unit::Volt));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "voltage_at_phase_3",
         Quantity::Voltage,
         DifVifKey("0AFDC9FC03"),
@@ -172,7 +172,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_STRING_FUNC(device_date_time_),
         GET_STRING_FUNC(device_date_time_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_tariff_1",
         Quantity::Energy,
         DifVifKey("8E1003"),
@@ -187,7 +187,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(total_energy_consumption_tariff_1_kwh_, Unit::KWH),
         GET_FUNC(total_energy_consumption_tariff_1_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_tariff_2",
         Quantity::Energy,
         DifVifKey("8E2003"),
@@ -203,7 +203,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         GET_FUNC(total_energy_consumption_tariff_2_kwh_, Unit::KWH));
 
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_tariff_3",
         Quantity::Energy,
         DifVifKey("8E3003"),
@@ -218,7 +218,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         SET_FUNC(total_energy_consumption_tariff_3_kwh_, Unit::KWH),
         GET_FUNC(total_energy_consumption_tariff_3_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_production_tariff_1",
         Quantity::Energy,
         DifVifKey("8E10833C"),
@@ -234,7 +234,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         GET_FUNC(total_energy_production_tariff_1_kwh_, Unit::KWH));
 
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_production_tariff_2",
         Quantity::Energy,
         DifVifKey("8E20833C"),
@@ -250,7 +250,7 @@ MeterAmiplus::MeterAmiplus(MeterInfo &mi, DriverInfo &di) : MeterCommonImplement
         GET_FUNC(total_energy_production_tariff_2_kwh_, Unit::KWH));
 
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_production_tariff_3",
         Quantity::Energy,
         DifVifKey("8E30833C"),
diff --git a/src/driver_apator08.cc b/src/driver_apator08.cc
index f83e126..47f10ac 100644
--- a/src/driver_apator08.cc
+++ b/src/driver_apator08.cc
@@ -42,7 +42,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterApator08::MeterApator08(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addField(
+    addNumericField(
         "total",
         Quantity::Volume,
         PrintProperty::JSON | PrintProperty::FIELD | PrintProperty::IMPORTANT,
diff --git a/src/driver_aventieshca.cc b/src/driver_aventieshca.cc
index fd5eaf2..707fc23 100644
--- a/src/driver_aventieshca.cc
+++ b/src/driver_aventieshca.cc
@@ -40,7 +40,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterAventiesHCA::MeterAventiesHCA(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "current_consumption",
         Quantity::HCA,
         NoDifVifKey,
@@ -55,7 +55,7 @@ MeterAventiesHCA::MeterAventiesHCA(MeterInfo &mi, DriverInfo &di) : MeterCommonI
         SET_FUNC(current_consumption_hca_, Unit::HCA),
         GET_FUNC(current_consumption_hca_, Unit::HCA));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "consumption_at_set_date",
         Quantity::HCA,
         NoDifVifKey,
@@ -76,7 +76,7 @@ MeterAventiesHCA::MeterAventiesHCA(MeterInfo &mi, DriverInfo &di) : MeterCommonI
         strprintf(key, "consumption_at_set_date_%d", i);
         strprintf(info, "Heat cost allocation at the %d billing period date.", i);
 
-        addFieldWithExtractor(
+        addNumericFieldWithExtractor(
             key,
             Quantity::HCA,
             NoDifVifKey,
diff --git a/src/driver_aventieswm.cc b/src/driver_aventieswm.cc
index aa3527d..a13553d 100644
--- a/src/driver_aventieswm.cc
+++ b/src/driver_aventieswm.cc
@@ -43,7 +43,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 MeterAventiesWM::MeterAventiesWM(MeterInfo &mi, DriverInfo &di) :
     MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -63,7 +63,7 @@ MeterAventiesWM::MeterAventiesWM(MeterInfo &mi, DriverInfo &di) :
         string msg, info;
         strprintf(msg, "consumption_at_set_date_%d", i);
         strprintf(info, "Water consumption at the %d billing period date.", i);
-        addFieldWithExtractor(
+        addNumericFieldWithExtractor(
             msg,
             Quantity::Volume,
             NoDifVifKey,
diff --git a/src/driver_c5isf.cc b/src/driver_c5isf.cc
index 6ea7e4a..8d061fd 100644
--- a/src/driver_c5isf.cc
+++ b/src/driver_c5isf.cc
@@ -70,7 +70,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
 {
     // Fields common for T1A1, T1A2, T1B...........
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         FIND_FIELD(MeasurementType::Instantaneous, VIFRange::EnergyWh),
@@ -79,7 +79,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(total_energy_kwh_, Unit::KWH),
         GET_FUNC(total_energy_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume",
         Quantity::Volume,
         FIND_FIELD(MeasurementType::Instantaneous, VIFRange::Volume),
@@ -152,7 +152,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
 
     for (int i=0; i<14; ++i)
     {
-        addFieldWithExtractor(
+        addNumericFieldWithExtractor(
             tostrprintf("prev_%d_month", i+1),
             Quantity::Energy,
             FIND_FIELD_S(MeasurementType::Instantaneous, VIFRange::EnergyWh, StorageNr(32+i)),
@@ -166,7 +166,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
 
     for (int i=0; i<14; ++i)
     {
-        addFieldWithExtractor(
+        addNumericFieldWithExtractor(
             tostrprintf("prev_%d_month", i+1),
             Quantity::Volume,
             FIND_FIELD_S(MeasurementType::Instantaneous, VIFRange::Volume, StorageNr(32+i)),
@@ -178,7 +178,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
 
     // Telegram type T1B ///////////////////////////////////////////////////////
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "due_energy_consumption",
         Quantity::Energy,
         FIND_FIELD_S(MeasurementType::Instantaneous, VIFRange::EnergyWh, StorageNr(8)),
@@ -196,7 +196,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_STRING_FUNC(due_date_),
         GET_STRING_FUNC(due_date_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "volume_flow",
         Quantity::Flow,
         FIND_FIELD(MeasurementType::Instantaneous, VIFRange::VolumeFlow),
@@ -205,7 +205,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(volume_flow_m3h_, Unit::M3H),
         GET_FUNC(volume_flow_m3h_, Unit::M3H));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "power",
         Quantity::Power,
         FIND_FIELD(MeasurementType::Instantaneous, VIFRange::PowerW),
@@ -214,7 +214,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(power_kw_, Unit::KW),
         GET_FUNC(power_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_last_month",
         Quantity::Energy,
         FIND_FIELD_S(MeasurementType::Instantaneous, VIFRange::EnergyWh, StorageNr(32)),
@@ -232,7 +232,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_STRING_FUNC(last_month_date_),
         GET_STRING_FUNC(last_month_date_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "max_power_last_month",
         Quantity::Power,
         NoDifVifKey,
@@ -247,7 +247,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(max_power_last_month_kw_, Unit::KW),
         GET_FUNC(max_power_last_month_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -262,7 +262,7 @@ MeterC5isf::MeterC5isf(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(flow_temperature_c_, Unit::C),
         GET_FUNC(flow_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "return_temperature",
         Quantity::Temperature,
         NoDifVifKey,
diff --git a/src/driver_iperl.cc b/src/driver_iperl.cc
index 36def53..5f617ed 100644
--- a/src/driver_iperl.cc
+++ b/src/driver_iperl.cc
@@ -53,7 +53,7 @@ MeterIperl::MeterIperl(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
     // version 0x68
     // version 0x7c Sensus 640
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -68,7 +68,7 @@ MeterIperl::MeterIperl(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_FUNC(total_water_consumption_m3_, Unit::M3),
         GET_FUNC(total_water_consumption_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "max_flow",
         Quantity::Flow,
         NoDifVifKey,
diff --git a/src/driver_itron.cc b/src/driver_itron.cc
index 0c83e9e..2b9b8a6 100644
--- a/src/driver_itron.cc
+++ b/src/driver_itron.cc
@@ -52,7 +52,7 @@ MeterItron::MeterItron(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
 
     addLinkMode(LinkMode::T1);
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -81,7 +81,7 @@ MeterItron::MeterItron(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementatio
         SET_STRING_FUNC(meter_date_),
         GET_STRING_FUNC(meter_date_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "target",
         Quantity::Volume,
         NoDifVifKey,
diff --git a/src/driver_lse_07_17.cc b/src/driver_lse_07_17.cc
index d19cc55..4d5a871 100644
--- a/src/driver_lse_07_17.cc
+++ b/src/driver_lse_07_17.cc
@@ -51,7 +51,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 MeterLSE_07_17::MeterLSE_07_17(MeterInfo &mi, DriverInfo &di) :
     MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -66,7 +66,7 @@ MeterLSE_07_17::MeterLSE_07_17(MeterInfo &mi, DriverInfo &di) :
         SET_FUNC(total_water_consumption_m3_, Unit::M3),
         GET_FUNC(total_water_consumption_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "due_date",
         Quantity::Volume,
         NoDifVifKey,
diff --git a/src/driver_microclima.cc b/src/driver_microclima.cc
index 71bc485..15c9102 100644
--- a/src/driver_microclima.cc
+++ b/src/driver_microclima.cc
@@ -47,7 +47,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         NoDifVifKey,
@@ -62,7 +62,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(total_energy_kwh_, Unit::KWH),
         GET_FUNC(total_energy_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_tariff1",
         Quantity::Energy,
         NoDifVifKey,
@@ -77,7 +77,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(total_energy_tariff1_kwh_, Unit::KWH),
         GET_FUNC(total_energy_tariff1_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume",
         Quantity::Volume,
         NoDifVifKey,
@@ -92,7 +92,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(total_volume_m3_, Unit::M3),
         GET_FUNC(total_volume_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume_tariff2",
         Quantity::Volume,
         NoDifVifKey,
@@ -107,7 +107,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(total_volume_tariff2_m3_, Unit::M3),
         GET_FUNC(total_volume_tariff2_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "volume_flow",
         Quantity::Flow,
         NoDifVifKey,
@@ -122,7 +122,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(volume_flow_m3h_, Unit::M3H),
         GET_FUNC(volume_flow_m3h_, Unit::M3H));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "power",
         Quantity::Power,
         NoDifVifKey,
@@ -137,7 +137,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(power_kw_, Unit::KW),
         GET_FUNC(power_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -152,7 +152,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(flow_temperature_c_, Unit::C),
         GET_FUNC(flow_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "return_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -167,7 +167,7 @@ MeterMicroClima::MeterMicroClima(MeterInfo &mi, DriverInfo &di) : MeterCommonImp
         SET_FUNC(return_temperature_c_, Unit::C),
         GET_FUNC(return_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "temperature_difference",
         Quantity::Temperature,
         NoDifVifKey,
diff --git a/src/driver_minomess.cc b/src/driver_minomess.cc
index 3b34369..4b8d98e 100644
--- a/src/driver_minomess.cc
+++ b/src/driver_minomess.cc
@@ -43,7 +43,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterMinomess::MeterMinomess(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -75,7 +75,7 @@ MeterMinomess::MeterMinomess(MeterInfo &mi, DriverInfo &di) : MeterCommonImpleme
         SET_STRING_FUNC(meter_date_),
         GET_STRING_FUNC(meter_date_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "target",
         Quantity::Volume,
         NoDifVifKey,
diff --git a/src/driver_piigth.cc b/src/driver_piigth.cc
index 6ba2bab..474f078 100644
--- a/src/driver_piigth.cc
+++ b/src/driver_piigth.cc
@@ -45,7 +45,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 MeterPIIGTH::MeterPIIGTH(MeterInfo &mi, DriverInfo &di) :
     MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -60,7 +60,7 @@ MeterPIIGTH::MeterPIIGTH(MeterInfo &mi, DriverInfo &di) :
         SET_FUNC(temperature_c_, Unit::C),
         GET_FUNC(temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "average_temperature_1h",
         Quantity::Temperature,
         NoDifVifKey,
@@ -75,7 +75,7 @@ MeterPIIGTH::MeterPIIGTH(MeterInfo &mi, DriverInfo &di) :
         SET_FUNC(average_temperature_1h_c_, Unit::C),
         GET_FUNC(average_temperature_1h_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "average_temperature_24h",
         Quantity::Temperature,
         NoDifVifKey,
@@ -91,7 +91,7 @@ MeterPIIGTH::MeterPIIGTH(MeterInfo &mi, DriverInfo &di) :
         GET_FUNC(average_temperature_24h_c_, Unit::C));
 
     /*
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "relative_humidity",
         Quantity::Temperature,
         DifVifKey("02FB1A"),
diff --git a/src/driver_qwater.cc b/src/driver_qwater.cc
index f7e36c1..9d1a198 100644
--- a/src/driver_qwater.cc
+++ b/src/driver_qwater.cc
@@ -52,7 +52,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 MeterQWater::MeterQWater(MeterInfo &mi, DriverInfo &di) :
     MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
@@ -67,7 +67,7 @@ MeterQWater::MeterQWater(MeterInfo &mi, DriverInfo &di) :
         SET_FUNC(total_water_consumption_m3_, Unit::M3),
         GET_FUNC(total_water_consumption_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "due_date",
         Quantity::Volume,
         NoDifVifKey,
@@ -96,7 +96,7 @@ MeterQWater::MeterQWater(MeterInfo &mi, DriverInfo &di) :
         SET_STRING_FUNC(due_date_),
         GET_STRING_FUNC(due_date_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "due_date_17",
         Quantity::Volume,
         NoDifVifKey,
diff --git a/src/driver_sharky.cc b/src/driver_sharky.cc
index 021262e..5c40ca1 100644
--- a/src/driver_sharky.cc
+++ b/src/driver_sharky.cc
@@ -46,7 +46,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         NoDifVifKey,
@@ -61,7 +61,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(total_energy_kwh_, Unit::KWH),
         GET_FUNC(total_energy_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption_tariff1",
         Quantity::Energy,
         NoDifVifKey,
@@ -76,7 +76,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(total_energy_tariff1_kwh_, Unit::KWH),
         GET_FUNC(total_energy_tariff1_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume",
         Quantity::Volume,
         NoDifVifKey,
@@ -91,7 +91,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(total_volume_m3_, Unit::M3),
         GET_FUNC(total_volume_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume_tariff2",
         Quantity::Volume,
         NoDifVifKey,
@@ -106,7 +106,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(total_volume_tariff2_m3_, Unit::M3),
         GET_FUNC(total_volume_tariff2_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "volume_flow",
         Quantity::Flow,
         NoDifVifKey,
@@ -121,7 +121,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(volume_flow_m3h_, Unit::M3H),
         GET_FUNC(volume_flow_m3h_, Unit::M3H));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "power",
         Quantity::Power,
         NoDifVifKey,
@@ -136,7 +136,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(power_kw_, Unit::KW),
         GET_FUNC(power_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -151,7 +151,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(flow_temperature_c_, Unit::C),
         GET_FUNC(flow_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "return_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -166,7 +166,7 @@ MeterSharky::MeterSharky(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementat
         SET_FUNC(return_temperature_c_, Unit::C),
         GET_FUNC(return_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "temperature_difference",
         Quantity::Temperature,
         NoDifVifKey,
diff --git a/src/driver_sharky774.cc b/src/driver_sharky774.cc
index 596228a..9e13d95 100644
--- a/src/driver_sharky774.cc
+++ b/src/driver_sharky774.cc
@@ -47,7 +47,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         NoDifVifKey,
@@ -62,7 +62,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(total_energy_consumption_kwh_, Unit::KWH),
         GET_FUNC(total_energy_consumption_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_volume",
         Quantity::Volume,
         NoDifVifKey,
@@ -77,7 +77,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(total_volume_m3_, Unit::M3),
         GET_FUNC(total_volume_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "volume_flow",
         Quantity::Flow,
         NoDifVifKey,
@@ -92,7 +92,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(volume_flow_m3h_, Unit::M3H),
         GET_FUNC(volume_flow_m3h_, Unit::M3H));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "power",
         Quantity::Power,
         NoDifVifKey,
@@ -107,7 +107,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(power_kw_, Unit::KW),
         GET_FUNC(power_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -122,7 +122,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(flow_temperature_c_, Unit::C),
         GET_FUNC(flow_temperature_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "return_temperature",
         Quantity::Temperature,
         NoDifVifKey,
@@ -137,14 +137,14 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(return_temperature_c_, Unit::C),
         GET_FUNC(return_temperature_c_, Unit::C));
 
-    addField("temperature_difference",
+    addNumericField("temperature_difference",
              Quantity::Temperature,
              PrintProperty::JSON | PrintProperty::FIELD,
              "The temperature difference.",
              [](Unit u, double v) {},
              [this](Unit u) { return flow_temperature_c_ - return_temperature_c_; });
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "operating_time",
         Quantity::Time,
         DifVifKey("0AA618"),
@@ -159,7 +159,7 @@ MeterSharky774::MeterSharky774(MeterInfo &mi, DriverInfo &di) :  MeterCommonImpl
         SET_FUNC(operating_time_h_, Unit::Hour),
         GET_FUNC(operating_time_h_, Unit::Hour));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "energy_at_set_date",
         Quantity::Energy,
         NoDifVifKey,
diff --git a/src/driver_supercom587.cc b/src/driver_supercom587.cc
index ae5476d..901e54c 100644
--- a/src/driver_supercom587.cc
+++ b/src/driver_supercom587.cc
@@ -41,7 +41,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterSupercom587::MeterSupercom587(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total",
         Quantity::Volume,
         NoDifVifKey,
diff --git a/src/driver_ultraheat.cc b/src/driver_ultraheat.cc
index f746a22..e320af4 100644
--- a/src/driver_ultraheat.cc
+++ b/src/driver_ultraheat.cc
@@ -43,7 +43,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "heat",
         Quantity::Energy,
         NoDifVifKey,
@@ -58,7 +58,7 @@ MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImple
         SET_FUNC(heat_mj_, Unit::MJ),
         GET_FUNC(heat_mj_, Unit::MJ));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "volume",
         Quantity::Volume,
         NoDifVifKey,
@@ -73,7 +73,7 @@ MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImple
         SET_FUNC(volume_m3_, Unit::M3),
         GET_FUNC(volume_m3_, Unit::M3));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "power",
         Quantity::Power,
         NoDifVifKey,
@@ -88,7 +88,7 @@ MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImple
         SET_FUNC(power_kw_, Unit::KW),
         GET_FUNC(power_kw_, Unit::KW));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow",
         Quantity::Flow,
         NoDifVifKey,
@@ -103,7 +103,7 @@ MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImple
         SET_FUNC(flow_m3h_, Unit::M3H),
         GET_FUNC(flow_m3h_, Unit::M3H));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "flow",
         Quantity::Temperature,
         NoDifVifKey,
@@ -118,7 +118,7 @@ MeterUltraHeat::MeterUltraHeat(MeterInfo &mi, DriverInfo &di) : MeterCommonImple
         SET_FUNC(flow_c_, Unit::C),
         GET_FUNC(flow_c_, Unit::C));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "return",
         Quantity::Temperature,
         NoDifVifKey,
diff --git a/src/driver_vario451mid.cc b/src/driver_vario451mid.cc
index 8ed2dac..9a905d5 100644
--- a/src/driver_vario451mid.cc
+++ b/src/driver_vario451mid.cc
@@ -42,7 +42,7 @@ static bool ok = registerDriver([](DriverInfo&di)
 
 MeterVario451Mid::MeterVario451Mid(MeterInfo &mi, DriverInfo &di) :  MeterCommonImplementation(mi, di)
 {
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "total_energy_consumption",
         Quantity::Energy,
         NoDifVifKey,
@@ -57,7 +57,7 @@ MeterVario451Mid::MeterVario451Mid(MeterInfo &mi, DriverInfo &di) :  MeterCommon
         SET_FUNC(total_energy_consumption_kwh_, Unit::KWH),
         GET_FUNC(total_energy_consumption_kwh_, Unit::KWH));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "energy_at_old_date",
         Quantity::Energy,
         NoDifVifKey,
@@ -86,7 +86,7 @@ MeterVario451Mid::MeterVario451Mid(MeterInfo &mi, DriverInfo &di) :  MeterCommon
         SET_STRING_FUNC(old_date_txt_),
         GET_STRING_FUNC(old_date_txt_));
 
-    addFieldWithExtractor(
+    addNumericFieldWithExtractor(
         "energy_at_set_date",
         Quantity::Energy,
         NoDifVifKey,
diff --git a/src/meters.cc b/src/meters.cc
index df1c78f..8f69c3a 100644
--- a/src/meters.cc
+++ b/src/meters.cc
@@ -793,8 +793,6 @@ void MeterCommonImplementation::addPrint(string vname, Quantity vquantity,
                   NULL,
                   NULL,
                   NULL,
-                  NULL,
-                  NULL,
                   NoLookup
             ));
 }
@@ -823,8 +821,6 @@ void MeterCommonImplementation::addPrint(string vname, Quantity vquantity, Unit
                   NULL,
                   NULL,
                   NULL,
-                  NULL,
-                  NULL,
                   NoLookup
             ));
 }
@@ -851,13 +847,11 @@ void MeterCommonImplementation::addPrint(string vname, Quantity vquantity,
                   getValueFunc,
                   NULL,
                   NULL,
-                  NULL,
-                  NULL,
                   NoLookup
             ));
 }
 
-void MeterCommonImplementation::addFieldWithExtractor(
+void MeterCommonImplementation::addNumericFieldWithExtractor(
     string vname,
     Quantity vquantity,
     DifVifKey dif_vif_key,
@@ -876,51 +870,6 @@ void MeterCommonImplementation::addFieldWithExtractor(
     string field_name = vname+"_"+default_unit;
     fields_.push_back(field_name);
 
-    // Compose the extract function.
-    function<bool(FieldInfo *p,Meter *m, Telegram *t)> extract =
-              [](FieldInfo *fi, Meter *m, Telegram *t)
-              {
-                  bool found = false;
-                  string key = fi->difVifKey().str();
-                  int offset {};
-                  if (key == "")
-                  {
-                      // Search for key.
-                      bool ok = findKeyWithNr(fi->measurementType(),
-                                              fi->vifRange(),
-                                              fi->storageNr().intValue(),
-                                              fi->tariffNr().intValue(),
-                                              fi->indexNr().intValue(),
-                                              &key,
-                                              &t->values);
-                      if (!ok) return false;
-                  }
-                  double extracted_double_value = NAN;
-                  if (extractDVdouble(&t->values,
-                                      key,
-                                      &offset,
-                                      &extracted_double_value,
-                                      fi->vifScaling() == VifScaling::Auto ||
-                                      fi->vifScaling() == VifScaling::AutoSigned,
-                                      fi->vifScaling() == VifScaling::NoneSigned ||
-                                      fi->vifScaling() == VifScaling::AutoSigned))
-                  {
-                      Unit decoded_unit = fi->defaultUnit();
-                      if (fi->vifRange() != VIFRange::Any &&
-                          fi->vifRange() != VIFRange::AnyVolumeVIF &&
-                          fi->vifRange() != VIFRange::AnyEnergyVIF &&
-                          fi->vifRange() != VIFRange::AnyPowerVIF &&
-                          fi->vifRange() != VIFRange::None)
-                      {
-                          decoded_unit = toDefaultUnit(fi->vifRange());
-                      }
-                      fi->setValueDouble(decoded_unit, extracted_double_value);
-                      t->addMoreExplanation(offset, fi->renderJson(&m->conversions()));
-                      found = true;
-                  }
-                  return found;
-              };
-
     prints_.push_back(
         FieldInfo(vname,
                   vquantity,
@@ -939,13 +888,11 @@ void MeterCommonImplementation::addFieldWithExtractor(
                   NULL,
                   setValueFunc,
                   NULL,
-                  extract,
-                  NULL,
                   NoLookup
             ));
 }
 
-void MeterCommonImplementation::addField(
+void MeterCommonImplementation::addNumericField(
     string vname,
     Quantity vquantity,
     PrintProperties print_properties,
@@ -975,8 +922,6 @@ void MeterCommonImplementation::addField(
                   NULL,
                   setValueFunc,
                   NULL,
-                  NULL,
-                  NULL,
                   NoLookup
             ));
 }
@@ -999,62 +944,6 @@ void MeterCommonImplementation::addStringFieldWithExtractor(
     string field_name = vname+"_"+default_unit;
     fields_.push_back(field_name);
 
-    // Compose the extract function.
-    function<bool(FieldInfo *p,Meter *m, Telegram *t)> extract =
-                  [](FieldInfo *fi, Meter *m, Telegram *t)
-                  {
-                      bool found = false;
-                      string key = fi->difVifKey().str();
-                      int offset {};
-                      if (key == "")
-                      {
-                          // Search for key.
-                          bool ok = findKeyWithNr(fi->measurementType(),
-                                                  fi->vifRange(),
-                                                  fi->storageNr().intValue(),
-                                                  fi->tariffNr().intValue(),
-                                                  fi->indexNr().intValue(),
-                                                  &key,
-                                                  &t->values);
-                          if (!ok) return false;
-                      }
-                      if (fi->vifRange() == VIFRange::DateTime)
-                      {
-                          struct tm datetime;
-                          extractDVdate(&t->values, key, &offset, &datetime);
-                          string extracted_device_date_time = strdatetime(&datetime);
-                          fi->setValueString(extracted_device_date_time);
-                          t->addMoreExplanation(offset, fi->renderJsonText());
-                          found = true;
-                      }
-                      else if (fi->vifRange() == VIFRange::Date)
-                      {
-                          struct tm date;
-                          extractDVdate(&t->values, key, &offset, &date);
-                          string extracted_device_date = strdate(&date);
-                          fi->setValueString(extracted_device_date);
-                          t->addMoreExplanation(offset, fi->renderJsonText());
-                          found = true;
-                      }
-                      else if (fi->vifRange() == VIFRange::EnhancedIdentification ||
-                               fi->vifRange() == VIFRange::FabricationNo)
-                      {
-                          string extracted_id;
-                          extractDVReadableString(&t->values, key, &offset, &extracted_id);
-                          fi->setValueString(extracted_id);
-                          t->addMoreExplanation(offset, fi->renderJsonText());
-                          found = true;
-                      }
-                      else
-                      {
-                          error("Internal error: Cannot extract text string from vif %s in %s:%d\n",
-                                toString(fi->vifRange()),
-                                __FILE__, __LINE__);
-
-                      }
-                      return found;
-                  };
-
     prints_.push_back(
         FieldInfo(vname,
                   vquantity,
@@ -1073,8 +962,6 @@ void MeterCommonImplementation::addStringFieldWithExtractor(
                   getValueFunc,
                   NULL,
                   setValueFunc,
-                  NULL,
-                  extract,
                   NoLookup
             ));
 }
@@ -1098,36 +985,6 @@ void MeterCommonImplementation::addStringFieldWithExtractorAndLookup(
     string field_name = vname+"_"+default_unit;
     fields_.push_back(field_name);
 
-    // Compose the extract function.
-    function<bool(FieldInfo *p,Meter *m, Telegram *t)> extract =
-                  [](FieldInfo *fi, Meter *m, Telegram *t)
-                  {
-                      bool found = false;
-                      string key = fi->difVifKey().str();
-                      int offset {};
-                      if (key == "")
-                      {
-                          // Search for key.
-                          bool ok = findKeyWithNr(fi->measurementType(),
-                                                  fi->vifRange(),
-                                                  fi->storageNr().intValue(),
-                                                  fi->tariffNr().intValue(),
-                                                  fi->indexNr().intValue(),
-                                                  &key,
-                                                  &t->values);
-                          if (!ok) return false;
-                      }
-                      uint64_t extracted_bits {};
-                      if (extractDVlong(&t->values, key, &offset, &extracted_bits))
-                      {
-                          string translated_bits = fi->lookup().translate(extracted_bits);
-                          fi->setValueString(translated_bits);
-                          t->addMoreExplanation(offset, fi->renderJsonText());
-                          found = true;
-                      }
-                      return found;
-                  };
-
     prints_.push_back(
         FieldInfo(vname,
                   vquantity,
@@ -1146,8 +1003,6 @@ void MeterCommonImplementation::addStringFieldWithExtractorAndLookup(
                   getValueFunc,
                   NULL,
                   setValueFunc,
-                  NULL,
-                  extract,
                   lookup
             ));
 }
@@ -2168,14 +2023,13 @@ bool isValidKey(string& key, MeterDriver mt)
 
 void FieldInfo::performExtraction(Meter *m, Telegram *t)
 {
-    if (extract_double_)
+    if (xuantity_ == Quantity::Text)
     {
-        extract_double_(this, m, t);
+        extractString(m, t);
     }
-
-    if (extract_string_)
+    else
     {
-        extract_string_(this, m, t);
+        extractNumeric(m, t);
     }
 }
 
@@ -2187,3 +2041,111 @@ DriverName MeterInfo::driverName()
     }
     return driver_name;
 }
+
+bool FieldInfo::extractNumeric(Meter *m, Telegram *t)
+{
+    bool found = false;
+    string key = difVifKey().str();
+    int offset {};
+    if (key == "")
+    {
+        // Search for key.
+        bool ok = findKeyWithNr(measurementType(),
+                                vifRange(),
+                                storageNr().intValue(),
+                                tariffNr().intValue(),
+                                indexNr().intValue(),
+                                &key,
+                                &t->values);
+        if (!ok) return false;
+    }
+    double extracted_double_value = NAN;
+    if (extractDVdouble(&t->values,
+                        key,
+                        &offset,
+                        &extracted_double_value,
+                        vifScaling() == VifScaling::Auto ||
+                        vifScaling() == VifScaling::AutoSigned,
+                        vifScaling() == VifScaling::NoneSigned ||
+                        vifScaling() == VifScaling::AutoSigned))
+    {
+        Unit decoded_unit = defaultUnit();
+        if (vifRange() != VIFRange::Any &&
+            vifRange() != VIFRange::AnyVolumeVIF &&
+            vifRange() != VIFRange::AnyEnergyVIF &&
+            vifRange() != VIFRange::AnyPowerVIF &&
+            vifRange() != VIFRange::None)
+        {
+            decoded_unit = toDefaultUnit(vifRange());
+        }
+        setValueDouble(decoded_unit, extracted_double_value);
+        t->addMoreExplanation(offset, renderJson(&m->conversions()));
+        found = true;
+    }
+    return found;
+}
+
+bool FieldInfo::extractString(Meter *m, Telegram *t)
+{
+    bool found = false;
+    string key = difVifKey().str();
+    int offset {};
+    if (key == "")
+    {
+        // Search for key.
+        bool ok = findKeyWithNr(measurementType(),
+                                vifRange(),
+                                storageNr().intValue(),
+                                tariffNr().intValue(),
+                                indexNr().intValue(),
+                                &key,
+                                &t->values);
+        if (!ok) return false;
+    }
+    uint64_t extracted_bits {};
+    if (lookup_.hasLookups())
+    {
+        if (extractDVlong(&t->values, key, &offset, &extracted_bits))
+        {
+            string translated_bits = lookup().translate(extracted_bits);
+            setValueString(translated_bits);
+            t->addMoreExplanation(offset, renderJsonText());
+            found = true;
+        }
+    }
+    else if (vifRange() == VIFRange::DateTime)
+    {
+        struct tm datetime;
+        extractDVdate(&t->values, key, &offset, &datetime);
+        string extracted_device_date_time = strdatetime(&datetime);
+        setValueString(extracted_device_date_time);
+        t->addMoreExplanation(offset, renderJsonText());
+        found = true;
+    }
+    else if (vifRange() == VIFRange::Date)
+    {
+        struct tm date;
+        extractDVdate(&t->values, key, &offset, &date);
+        string extracted_device_date = strdate(&date);
+        setValueString(extracted_device_date);
+        t->addMoreExplanation(offset, renderJsonText());
+        found = true;
+    }
+    else if (vifRange() == VIFRange::EnhancedIdentification ||
+             vifRange() == VIFRange::FabricationNo)
+    {
+        string extracted_id;
+        extractDVReadableString(&t->values, key, &offset, &extracted_id);
+        setValueString(extracted_id);
+        t->addMoreExplanation(offset, renderJsonText());
+        found = true;
+    }
+    else
+    {
+        error("Internal error: Cannot extract text string from vif %s in %s:%d\n",
+              toString(vifRange()),
+              __FILE__, __LINE__);
+
+    }
+    return found;
+}
diff --git a/src/meters.h b/src/meters.h
index 17a6b85..1f4428b 100644
--- a/src/meters.h
+++ b/src/meters.h
@@ -326,8 +326,6 @@ struct FieldInfo
               function<string()> get_value_string,
               function<void(Unit,double)> set_value_double,
               function<void(string)> set_value_string,
-              function<bool(FieldInfo*, Meter *mi, Telegram *t)> extract_double,
-              function<bool(FieldInfo*, Meter *mi, Telegram *t)> extract_string,
               Translate::Lookup lookup
         ) :
         vname_(vname),
@@ -347,8 +345,6 @@ struct FieldInfo
         get_value_string_(get_value_string),
         set_value_double_(set_value_double),
         set_value_string_(set_value_string),
-        extract_double_(extract_double),
-        extract_string_(extract_string),
         lookup_(lookup)
     {}
 
@@ -374,6 +370,8 @@ struct FieldInfo
     void setValueDouble(Unit u, double d) { if (set_value_double_) set_value_double_(u, d);  }
     void setValueString(string s) { if (set_value_string_) set_value_string_(s); }
 
+    bool extractNumeric(Meter *m, Telegram *t);
+    bool extractString(Meter *m, Telegram *t);
     void performExtraction(Meter *m, Telegram *t);
 
     string renderJsonOnlyDefaultUnit();
@@ -402,8 +400,6 @@ private:
     function<string()> get_value_string_; // Callback to fetch the value from the meter.
     function<void(Unit,double)> set_value_double_; // Call back to set the value in the c++ object
     function<void(string)> set_value_string_; // Call back to set the value string in the c++ object
-    function<bool(FieldInfo*, Meter *mi, Telegram *t)> extract_double_; // Extract field from telegram and insert into meter.
-    function<bool(FieldInfo*, Meter *mi, Telegram *t)> extract_string_; // Extract field from telegram and insert into meter.
     Translate::Lookup lookup_;
 };
 
diff --git a/src/meters_common_implementation.h b/src/meters_common_implementation.h
index f4c9e47..4d05965 100644
--- a/src/meters_common_implementation.h
+++ b/src/meters_common_implementation.h
@@ -95,7 +95,7 @@ protected:
 #define FIND_SFIELD_STI(TYPE,INFO,STORAGE,TARIFF,INDEX) NoDifVifKey,TYPE,INFO,STORAGE,TARIFF,INDEX
 
 
-    void addFieldWithExtractor(
+    void addNumericFieldWithExtractor(
         string vname,          // Name of value without unit, eg total
         Quantity vquantity,    // Value belongs to this quantity.
         DifVifKey dif_vif_key, // You can hardocde a dif vif header here or use NoDifVifKey
@@ -110,7 +110,7 @@ protected:
         function<void(Unit,double)> setValueFunc, // Use the SET macro above.
         function<double(Unit)> getValueFunc); // Use the GET macro above.
 
-    void addField(
+    void addNumericField(
         string vname,          // Name of value without unit, eg total
         Quantity vquantity,    // Value belongs to this quantity.
         PrintProperties print_properties, // Should this be printed by default in fields,json and hr.