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Installation & User Manual
June 2013 Ed 19UK
Page 23 of 28
Recalibrating Gauge Transmitter using Vacuum (for gauge transmitters only)
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
potentiometer.
6. Increase the vacuum equal to the maximum height of the fluid (water gauge) and adjust the
output 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.