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GT_8-IOM Rev. 0 7/19
Printed in USA
THIS INFORMATION IS SUBJECT TO THE CONTROLS OF THE EXPORT ADMINISTRATION REGULATIONS (EAR). THIS INFORMATION SHALL NOT BE PROVIDED TO
NON-US PERSONS OR TRANSFERRED BY ANY MEANS TO ANY LOCATION OUTSIDE THE UNITED STATES CONTRARY TO THE REQUIREMENTS OF THE EAR.
CALIBRATION AND ADJUSTMENTS
For adjustment and/or calibration verification, use the following
calibration procedure:
1. Connect the required air supply pressure (25 psig for the
GT18 and GT28, 35 psig for all others) to the inlet of the
transducer, and a pressure gauge to the outlet.
2. Connect the electrical input and set the input signal to the
0% value (e.g. 4 mA for a direct acting 4-20 mA unit).
3. Observe the output pressure. Adjust if necessary by
turning the external zero adjust screw located under the
cap near the output pressure connection.
4. Increase the electrical input signal to the 100% value (e.g.
20 mA for a direct acting 4-20 mA unit).
5. Observe the output pressure. If adjustment is necessary,
remove the cover cap and adjust the range potentiometer
on the circuit board to obtain the required output.
6. The zero and range adjustments are interactive. After
adjusting the range potentiometer it will be necessary to
recheck the zero. Repeat steps 2 through 5 until both
endpoints are at the required values.
MAINTENANCE
Under normal conditions, no maintenance should be required. If
disassembly is necessary, refer to PNEUMATIC
TROUBLESHOOTING section of this document. It is important
that clean, dry air be supplied to the unit at all times. An ITT
Conoflow FR95 series Airpak (filter regulator) or equivalent
filtered air supply can be used to supply this I/P transducer
For pressure relay equipped models (GT28, GT48, or GT68)
periodically inspect the diaphragm assembly to see if the
diaphragm assembly shows signs of wear. To inspect, remove
the six (6) machine screws from the relay. While the relay is
disassembled from the I/P transducer, check freedom of
movement of the relay valve, and remove any foreign matter
which may have accumulated. When reassembling the relay, be
sure to properly orient the relay body to align the feed hole from
the inlet port to the fixed orifice in the housing cap. Tighten the
six (6) machine screws to 24 in-lb.
For replacement components, contact the factory with the full
model number and serial number of the product that parts are
required for.
TROUBLESHOOTING
PNEUMATIC
1. Check supply pressure. It should be constant 25 psig
(172 kPa) for the GT18 or GT 28 models, or a constant 35
psig (241 kPa) for all other models.
2. Make sure that tubing connections are tight.
3. Check zero and span calibration as previously outlined.
4. Check to see if housing body screen or flame arrestor (XP
version) is obstructed.
5. If disassembly is necessary, it must be done in a clean
work area. Should foreign debris become lodged between
the coil assembly and the magnet assembly, a malfunction
may occur. Removal of the magnet assembly will destroy
the calibration of the nozzle and balance beam
relationship.
6. If resonance (humming) is experienced, check outlet
piping to be sure it meets the minimum requirements
specified under INSTALLATION.
ELECTRICAL
1. Check to see that the input signal leads are connected to
proper terminals (see ELECTRICAL CONNECTION
section).
2. Make sure there are no loose wires at terminal or solder
connections.
3. Some field calibrators may not be able to supply sufficient
current to this transducer. Verify the input DC mA signal
using a digital ammeter.
4. Check input impedance by connecting an ohm meter to
terminals 1 and 2. In making any resistance tests, the
input signal wires from the controller (mA source) must be
disconnected. Nominal total input impedance of the 4-20
mA unit is 145 ohms. Nominal total input impedance of
the 10-50 mA unit is 60 ohms. Do not change the setting
of the range adjust potentiometer on the printed circuit
board when performing input impedance test.
5. A measure of resistance between any terminal of the
transducer and the external case should indicate an
“open” circuit. If resistance is indicated, coil windings or
the leads to the voice coil may be touching the case.
Further checks must then be made.
6. Remove housing from the transducer and disconnect the
coil lead plug from the circuit board. Check the
impedance of the coil. Nominal impedance is
approximately 150 ohms.
EXPLOSIONPROOF MODEL INFORMATION
FM Approvals lists the explosionproof model as
XP / I / 1 / BCD / T6 Ta = 60°C
DIP / II / 1 / EFG / T6 Ta = 60°C
