Setra System Model 276 - Manual

Operating Instructions
Model 276 Barometric Pressure Sensor
General Information
Your Setra transducer has been carefully calibrated before shipment to you and it should be handled with
the same care given any precision instrument. Accuracy and dimensions are reported on the specifica-
tions bulletin for the transducer.
The label on the unit specifies the calibrated output voltages at the low end and the high end of its pres-
sure ranges.
Ambient Conditions
Do not use in ambient conditions corrosive to the stainless steel housing or PVC jacketed cable, sub-
merge in liquids, or subject to spray or vibration environment.
Electrical Connections:
“Belden” Cable Lead
Function (#8723 Grey Cable)
positive excitation Red
positive output Green
negative output White
negative excitation Black
case Shield
Electrical
The electrical circuit is a 3-terminal circuit. Separate leads for negative output and negative excitation are
provided for convenience in wiring but are internally commoned. Use of these leads also avoids errors in
voltage readings caused by ground loops which can occur on 3 wire devices.
The pressure transducer should be operated with the shield connected either to the negative excitation
wire or to the negative output wire. Failure to do this may result in unsatisfactory operation of the unit.
NOTE: The circuit is not protected against mis-wiring. Use extreme care in wiring the positive
excitation voltage only to the red wire, and to ensure all four leads are correctly connected before
applying power. REVERSED OR MIS-WIRED EXCITATION MAY CAUSE PERMANENT DAMAGE TO
THE TRANSDUCER.
In some instances, use of long cables (several hundred feet long) may introduce enough cable capaci-
tance into the output circuit to cause output oscillation. If encountered, this oscillation may be eliminated
by connecting a 100 ohm resistor (1/8 watt or larger) in series to each of the output leads at the end of the
2 foot transducer cable. These series resistors add to the output resistance
Calibration
This unit has been precision calibrated at the factory. It has been designed to be inherently stable;
recalibration adjustments are not normally field accessible. If you do wish to perform a recalibration, and
have access to a high accuracy primary pressure standard, call the factory for instructions on field access
to the calibration adjustments.