Instrumentation field handbook

Connection: meter in series at an approved break or test point.

1. Confirm the loop can be opened and identify the effect on indication, control and trips.
2. Black lead to COM; red lead to the fused mA input; select DC mA.
3. Open the approved point and bridge the gap through the meter so all loop current passes through it.
4. Verify polarity, read the value, then remove the meter and fully restore the original conductor path.
5. Confirm the loop indication and affected logic return to normal.

Do not: connect across positive and negative like a voltmeter. That can short the loop or rupture the meter fuse.

Connection: meter in parallel across two defined points while the loop remains intact.

1. Black lead to COM; red lead to V/Ω; select DC volts.
2. Confirm the expected voltage and meter rating.
3. Place the leads across the supply, transmitter terminals, resistor or input points identified by the loop drawing.
4. Compare measured polarity and voltage with the expected loop-power distribution.
5. Remove probes without disturbing conductors and confirm covers or test points are restored.

Use for: checking supply presence, voltage drop and whether enough voltage remains for the transmitter and barriers.

Connection: calibrator becomes the current source for an isolated receiving circuit.

1. Obtain approval for simulation and identify every display, alarm, trip, permissive or control action affected.
2. Isolate the field transmitter at the authorised boundary.
3. Connect source positive and negative to the receiving circuit with the documented polarity.
4. Select source mA and apply approved points such as 4, 8, 12, 16 and 20 mA.
5. Verify indication and logic at each point, return to a safe value, disconnect and restore field wiring.

Do not: source into a circuit that is still being actively driven by another source.

Connection: calibrator controls current but uses the loop’s existing external power.

1. Confirm the loop power remains available and the transmitter can be removed from the circuit.
2. Connect the calibrator at the authorised transmitter boundary with correct polarity.
3. Select mA simulate—not source or measure.
4. Apply the required current points and verify the complete receiving path.
5. Return to a safe value, disconnect, restore the transmitter and confirm live operation.

Difference: simulate needs external loop power; source mode supplies the current itself.

Connection: calibrator supplies loop power and measures current in the same isolated circuit.

1. Isolate the transmitter from site loop power and verify the approved bench or field-test boundary.
2. Connect loop-power positive to transmitter positive and the return path to the calibrator negative input as shown by the manufacturer.
3. Select loop-power/mA mode and confirm the configured supply voltage.
4. Apply the process input and compare transmitter current with the expected output.
5. Remove loop power before disconnecting, then restore original wiring and site power.

Do not: apply calibrator loop power on top of an energised site supply.

Connection: communicator in parallel across an approved loop point; analogue current remains complete.

1. Confirm the device is HART-capable and communication is permitted.
2. Connect communicator leads across the transmitter or approved resistor/test points.
3. Verify the loop has the required resistance and stable power for communication.
4. Read identity, range, units, damping and diagnostics before changing anything.
5. Make only authorised configuration changes, save evidence and verify the analogue output afterward.

Remember: successful digital communication does not prove the process sensor or 4–20 mA path is accurate.

Connection: rated pressure source and reference on the process side; suitable mA measurement or loop-power mode on the electrical side.

1. Prove process isolation, depressurisation and the safe vent path.
2. Fit rated hoses and adapters without loading the transmitter body or manifold.
3. Leak-check the pressure setup before applying test points.
4. Apply pressure upscale and downscale while recording input, mA output and control-system indication.
5. Vent safely, remove pressure, restore valves and fittings, leak-check and confirm live indication.

DP units: follow the approved manifold sequence and protect the low-pressure side from overpressure.

Connection: calibrator at the authorised sensor terminal boundary using the configured sensor type and wire arrangement.

1. Confirm RTD type and 2/3/4-wire arrangement, or thermocouple type and cold-junction method.
2. Disconnect the field sensor only after recording the as-found condition.
3. Black and red leads use the V/Ω or dedicated temperature terminals required by the calibrator.
4. Select the exact sensor type and apply approved temperature points across the range.
5. Restore polarity and lead arrangement, tighten correctly, close the enclosure and verify ambient process indication.

Do not: mix thermocouple extension materials, ignore cold-junction compensation or short out RTD lead compensation.