420PRO is a non-isolated, easy-to-use 2-wire transmitter for in-head mounting in DIN B and similar heads.
Reduced height simplifies mounting in low connection heads. Configuration is made in seconds with the user-friendly 420PRO software. No external power is needed.
420PRO is programmable for RTD’s in 3 and 4-wire connection as well as for 11 T/C types. Useful error correction functions improve the accuracy.
Unit of Measure

Input RTD

Input RTD - Ni 100 (DIN 43760), 3-, 4-Wire Connection

N/A -60 to +250 ºC-76 to +482 ºF

Input RTD - Ni 1000 (DIN 43760), 3-, 4-Wire Connection

N/A -100 to +150 ºC-148 to +302 ºF

Input RTD - Pt 100 (IEC 60751, α = 0.00385), 3-, 4-Wire Connection

N/A -200 to +1000 ºC-328 to +1832 ºF

Input RTD - Pt 100 (JIS C 1604, α = 0.003916), 3-, 4-Wire Connection

N/A -200 to +1000 ºC-328 to +1832 ºF

Input RTD - Pt 100 (US, α = 0.003902), 3-, 4-Wire Connection

N/A -200 to +1000 ºC-328 to +1832 ºF

Input RTD - Pt 1000 (IEC 60751, α = 0.00385), 3-, 4-Wire Connection

N/A -200 to +200 ºC-328 to +392 ºF

Input RTD - PtX (IEC 60751, α = 0.00385), 3-, 4-Wire Connection

N/A Any Pt Function between Pt 10 - Pt 1000

Sensor Current

N/A ~ 0.4 mA

Max. Sensor Wire Resistance

N/A 25 Ohms per Wire

Input Thermocouples

Input Thermocouple Type

N/A AE, B, E, J, K, L, N, R, S, T, U (Acc. to T/C Standards)

Max. Sensor Wire Resistance  

N/A (Total Loop) 500 Ohm


Sensor Failure Monitoring

N/A Upscale or Downscale Action


Zero Adjustment

N/A All Inputs - Any Value within Range Limits

Min. Span

N/A Pt100 18 ºFPt100 10 ºCT/C 2 mV


Analog Output

N/A 4 to 20 mA (Temperature Linear)


N/A 5 µA

Min. Output Signal

N/A Failure: 3.5 mAMeasurement: 3.8 mA

Max. Output Signal

N/A Failure: 21.6 mAMeasurement: 20.5 mA

Permissible Load

N/A 725 Ohms at 24 VDC 420pro-load-diagram.JPG


Ambient Temperature

N/A -40 to 185 ºF-40 to 85 ºC

Storage & Operating Temperature

N/A -40 to 185 ºF-40 to 85 ºC

General Data

Selectable Dampening Time

N/A ~ 2 s

Update Time

N/A ~ 1.5 s

Isolation In - Out

N/A Non-Isolated


N/A 0 to 100% RH


N/A Acc. to IEC 60068-2-6, Test Fc, 60 to 500 Hz, 10 g

Power Supply (Polarity Protected)

Supply Voltage

N/A 8 to 32 VDC

Permissible Ripple

N/A 4V p-p at 50 / 60 Hz


Linearity1 N/A RTD ±0.1 %T/C ±0.2 %
Calibration2 N/A RTD Max. of ±0.2 ºC / ±0.4 ºF or ±0.1 % T/C Max. of ±20 µV or ±0.1 %

Cold Junction Compensation (CJC)

N/A T/C ±0.9 ºFT/C ±0.5 ºC
Temperature Influence3 N/A All Inputs Max. of ±0.25ºC / 25ºC or ±0.25% / 25ºC All Inputs Max. of ±0.5ºF / 50ºF or ±0.28% / 50ºF
Temperature Influence CJC4 N/A T/C ±0.5ºC / 25ºC T/C ±1.0ºF / 50ºF
RFI Influence (0.15 to 1,000 MHz, 10V or V/m)5 N/A ±0.5% (Typical)
Long-Term Stability6 N/A ±0.2% per Year




Flammability (UL)

N/A PA, V0


N/A DIN B-Head or Larger, DIN Rail (w/ Mounting Kit)


N/A Single / Stranded Wires Max. 1.5 mm2, AWG 16


N/A 32 g

Housing Protection / Terminal Protection

N/A IP 65 / IP 00


N/A Measurements with RTD's in 3 and 4-wire connection
420PRO accepts inputs from a number of standardized RTD's such as Pt100, Pt500 and Pt1000 acc. to IEC 60751 (a=0.00385), Pt100 acc. to JIS C 1604 (a=0.003916) and US standards (a=0.003902) as well as Ni100 and Ni1000 acc. to DIN 43760. 3 and 4-wire connection can be selected.

Measurements with Thermocouples
420PRO accepts inputs from 11 types of standardized Thermocouples. For T/C input, the CJC (Cold Junction Compensation) is fully automatic, by means of an accurate measurement of the terminal temperature. Alternately, the CJC can be disabled.

Temperature linear output
Fully temperature linear 4-20 mA output for RTD's and Thermocouples.

Designed for harsh conditions
Rugged design tested for 10 g vibrations.

NAMUR compliant
Output limitations and fail currents according to NAMUR recommendations.

Sensor matching and error corrections for maximum accuracy
A matching to a calibrated temperature sensor can easily be performed with the Sensor Error Compensation function. The System Error Compensation is a convenient way to adjust the sensor/transmitter combination (or just the transmitter) for highest accuracy in a certain measuring range.

Mounting, wiring and testing
420PRO is designed to fit inside connection heads type DIN B or larger. The large center hole, dia. 7 mm/0.28 inch, the robust terminals with test connections and the low height greatly simplify the mounting, wiring and testing procedure.

Configuration without external power
Edit or read the configuration off-line by just connecting to the USB port of a PC.

420PRO, easy-to-use Windows configuration
The simple and user-friendly 420PRO software is used for transmitter configuration in seconds. In one window all parameters are set, such as sensor type, measuring range, filter activation, CJC, sensor failure action, error corrections, etc.

  • 1 Of Input Span
  • 2 Of Input Span
  • 3 Of Input Span
    If Zero-Deflection -> 100% of Input Span: Add 0.125% of Input Span / 25 °C or 0.14% of Input Span / 50 °F per 100% Zero-Deflection
    Reference Temperature 20 °C / 68 °F
  • 4 Reference Temperature 20 °C / 68 °F
  • 5 Of Input Span
  • 6 Of Input Span