There are many factors that cause shifts in the calibration of a pressure sensor. These include temperature, barometric pressure, field elevation, pressure offsets, heavy cycling and even the lack of sensor use.
When these factors affect your sensor’s calibration, it is generally cause to send the sensor back to the manufacturer for service. This costs valuable time and money.
Calibration involves two key reference points, the zero and the span. Many of the issues resulting from the factors listed above can be resolved by resetting your zero point (4mA). The PT-500 submersible pressure transducer lets you do this in the field. Here’s where the magnet comes into play:
The zero point can be adjusted by holding a magnet close to the can, about 1 ½ inches from the top or bottom of the can. It can be adjusted +/- 1 mA, or from 3 to 5 mA.
Holding the magnet perpendicular near the top increases the output.
Holding the magnet perpendicular near the bottom decreases the output.
If the zero output values do not change right away, follow the steps below:
1. Hold the magnet in place near the top of the can until the values change, up to two minutes.
2. If there is no change repeat the procedure near the bottom of the can.
3. If there is still no change, consult the factory.
By adjusting the PT-500 in the field, you are able to fine tune the 4mA (zero) point as needed for your application, without the expense and lost time of sending the sensor out for calibration.
As always, let us know if you have any questions. The PT-500 is the only submersible pressure sensor on the market that let's you do this - so we understand.