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98MANALX18 Rev. B 9/4/14
SHUNT CALIBRATION
The Model 118 is equipped with an external shunt calibration. This feature allows field calibration to be performed by
electrically simulating pressure. When the shunt calibration is activated, the transducer bridge is unbalanced by an amount
equivalent to the application of approximately 80% of full scale pressure. The exact pressure and output values are listed
on the Performance Certificate.
External shunt calibration is achieved by placing the specified resistor across Pins 2 and 4 of the electrical connector. The
value of the resistor is listed on the Performance Certificate. Internal shunt calibration is optional on the Model 118. Units
with internal shunt calibration have a 6 pin connector. The shunt calibration resistor is built into the transducer and the
circuit is activated by connecting (shorting) Pins 5 and 6 of the connector.
After calibration, the shunt calibration circuit should be deactivated for normal operation.
FIELD CALIBRATION
The Model 218 Series Transducers are provided with a unique feature that permits field calibration to be performed without
the need of a pressure source, by electronically simulating pressure. The nylon access screws should be removed and the
pressure port shall be vented to zero pressure. For transducers measuring absolute pressure, a full vacuum must be
applied to the pressure port. Connecting (shorting) the calibration terminals (Pins 5 and 6), produces an output equivalent to
approximately 80% of full-scale pressure. Refer to the performance certificate, which was supplied with the transducer, for
the exact calibration output. If the certificate is unavailable, the calibration output can be calculated by using the following
formula: Volts DC = (Cal pressure from transducer label / pressure range) x 5. Thus, following adjustment of zero output for
zero pressure, the calibration circuit may be activated and the gain or span adjustment screw can be turned until the correct
calibration output appears at the output terminals. The calibration terminals should then be disconnected and the zero
adjustment reconfirmed.
Note - the calibration circuit shall be deactivated during normal operation. The nylon cover screws,
removed to access zero and span adjustments, shall be reinstalled after calibrating the transducer.
Summary of Contents for 118
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