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Reference Manual MAS2600: Testing and Recalibration
Ed 21 December 2014
40
Recalibrating Gauge Transmitter using Vacuum (for gauge
transmitters only)
Caution! Please observe that testing and recalibration of transmitters mounted in hazardous
areas shall be carried out by Ex qualified personnel.
An internally mounted transducer can also be recalibrated by using vacuum.
1. Check that the tank is empty.
2. Check that the range select switch on the amplifier is correctly set.
3. Set the calibrator to vacuum mode.
4. Connect the hose from the calibrator to the breather tube from the transducer cable.
5. In conditions of no pressure the output signal should be adjusted to 4.00 mA on the zero poten-
tiometer.
6. Increase the vacuum equal to the maximum height of the fluid (water gauge) and adjust the out-
put signal to 20.00 mA on the span potentiometer.
7. Remove the vacuum and check the zero point.
8. Check the linearity at 0-25-50-75 and 100% of the measuring range.
9. If necessary, repeat the steps 5 to 8.
Note! If the calibrated maximum water gauge is greater than the maximum water gauge that
can be generated by the vacuum calibrator, the proportional mA output signal equal to
the maximum vacuum signal should be calculated.
Example:
If the full-scale of the transmitter is 15 mH
2
O, and the maximum capacity of the vacuum calibrator is
7.5 mH
2
O, the mA output signal at 7.5 mH
2
O is calculated as:
15 mH
2
O = 20 mA and 0 mH
2
O = 4 mA
7.5 mH
2
O = 4 + ((20 - 4)
*
7.5) / 15 = 12 mA
The span potentiometer is adjusted so that the output signal shows 12 mA at 7.5 mH
2
O.