How to choose the right process calibrator
A process calibrator measures and simulates the signals that run process plants: the mA loop, thermocouples and Pt100. This guide explains what matters for accuracy, features and HART communication, and how to trim transmitters right on site.
View process calibratorsWhich signals must a process calibrator handle?
The backbone of process control is the 4‑20 mA current loop. A good process calibrator measures this current, sources it actively and can power the loop with 24 V. This is complemented by temperature signals from thermocouples and resistance thermometers such as the Pt100.
For thermocouples the unit should cover at least types J, K, T, E, N, R, S and B, each with internal cold-junction compensation. For RTD sensors, Pt100 and Pt1000 matter as well as 2-, 3- and 4-wire connection to compensate lead resistance cleanly.
- Current: measure and source 0‑24 mA with 24 V loop supply.
- Voltage: mV for thermocouples, V for standard signals up to 30 V.
- Thermocouples: types J, K, T, E, N, R, S, B with cold junction.
- RTD: Pt100 and Pt1000 in 2-, 3- and 4-wire configuration.
- Frequency and resistance for additional sensor types.
Measure, simulate, trim - what does it mean?
A process calibrator works in two directions. In measure mode it reads the real signal of a sensor or transmitter. In simulate or source mode it generates a precise reference signal that mimics a given sensor input for the device under test.
This lets you trim a temperature transmitter on site without bringing the process to real temperatures: the calibrator simulates a Pt100 at 0 °C and 100 °C at the input while it measures the 4‑20 mA output at the same time. Any deviation is corrected on the transmitter using zero and span.
Basics of Pt100, thermocouples and cold-junction compensation.
Read the guideWhat matters for accuracy and HART?
A calibrator must be clearly more accurate than the item it checks. A rule of thumb is a test uncertainty ratio (TUR) of at least 4:1. For a transmitter in the 0.1 % class the calibrator should therefore reach about 0.025 % or better.
The figure is usually given as percent of reading plus digits, or plus percent of full scale. Watch the stated temperature range and the calibrator's own recalibration interval so the factory calibration stays valid. For modern field devices an integrated HART communicator is useful to read parameters and perform digital trimming.
- Test uncertainty ratio of at least 4:1 versus the device under test.
- Base mA accuracy usually 0.01‑0.02 % of reading.
- Switchable 250 Ω HART resistor for communication.
- Rugged housing with IP rating for harsh field use.
- Traceable factory certificate to ISO/IEC 17025 as proof.
Frequently asked questions
What is the difference between a process calibrator and a multimeter?
A multimeter only measures. A process calibrator measures and also generates standard reference signals such as 4‑20 mA or Pt100 to feed and trim transmitters on purpose.
Can I trim a transmitter on site without real temperature?
Yes. The calibrator simulates the sensor signal at the input, for example Pt100 at 100 °C, and measures the 4‑20 mA output at the same time. That way you correct zero and span without a real process value.
How accurate does my calibrator need to be?
It should be about four times more accurate than the device under test. For 0.1 % class field devices a base accuracy around 0.02 % is a sensible target.
What is the 24 V loop supply for?
It powers a two-wire transmitter so you can test it without a separate power source and measure the output current in the same loop.
Looking for the right process calibrator?
We supply process calibrators for the mA loop, thermocouples and Pt100 with loop supply and HART - traceably calibrated to ISO/IEC 17025.
Traceable
Factory certificate to ISO/IEC 17025 included.
Full feature set
mA, mV, RTD and thermocouples in one instrument.
Field ready
Rugged IP-rated housings for plant operation.
Expert advice
Our specialists help you choose.