Sample
DP Transmitter Calibration: Safe Isolation to 5-Point Test
Do the job like a technician: 1 Safety, 2 Pick tools, 3 Connect, 4 Calibrate (5 points up and down), 5 Restore. Click the valves on the picture, pick the tools, press the buttons. Mistakes show what really happens. Use Next step to move on.
Procedure map (click a step)
Hint
1 Safety first
Tick the three safety items, then click the valves on the picture in the safe order.
Live bench readings
| Applied pressure | |
| Standard mA | |
| Multimeter (cross-check) | |
| Difference | |
| HART digital PV | |
| mA converted to % |
Results table
| Point | Ideal mA | Up mA | Down mA | Err up | Err dn |
|---|
Error in % of span. Blue = rising, orange dashed = falling, green band = allowed error. A flat line near zero means a good transmitter.
Calibration certificate
| As-found worst error | |
| As-left worst error | |
| Up/down difference (hysteresis) | |
| Standard ratio (TUR) | |
| Result |
Typical practice (follow your site procedure): traceable standards, TUR 4:1 or better, 5 points rising then falling, record as-found before any adjustment, then as-left after.
Which instrument for which job
| Instrument | Use it for | Remember |
|---|---|---|
| Hand pump + test gauge | Quick field check | Not accurate enough to calibrate |
| Pressure calibrator + module | Standard in the field | Pick a module near the transmitter range |
| Deadweight tester | Lab reference | Very accurate, slow, needs a stable bench |
| Pressure controller | Automatic, repeatable tests | Costly, needs clean gas supply |
| Loop calibrator (mA) | Measure and power the loop | Use as the mA standard |
| Multimeter | Cross-check the mA | Never the main standard; always in series |
| HART communicator | Trim, re-range, read digital PV | Compare PV with mA to find a DAC error |
