Five-Point Calibration
After you have completed a calibration it is important to do a five-point calibration to ensure linearity. First, compare the transmitter output to the corresponding inputs, 0%, 25%, 50%, 75% and 100%. For example, if 25% of the input range is applied to a pneumatic pressure transmitter it should output 6 PSI. if 50% of the input range is applied to an electric pressure transmitter it should output 12mA.
Next, check your values going down the scale, 100%,75%,50%,25%, and 0%. Your values may be different going up then going down the scale. This error is called hysteresis. Hysteresis can be caused by many things such as elastic deformation, temperature change, or friction.
If your values going up and down the scale are within an acceptable error range then your transmitter is ready to be put in the field. If not, carefully examine the transmitter checking for any wear or damage. If you still can’t get within an acceptable error range then it may be time to replace the transmitter.
| Output in % | Output in mA | Output in PSI |
| 0 | 4 | 3 |
| 25 | 8 | 6 |
| 50 | 12 | 9 |
| 75 | 16 | 12 |
| 100 | 20 | 15 |
If your values going up and down the scale are within an acceptable error range then your transmitter is ready to be put in the field. If not, carefully examine the transmitter checking for any wear or damage. If you still can’t get within an acceptable error range then it may be time to replace the transmitter.
That’s about all when it comes to calibrating a transmitter!
