Setra System Model 204D - Manual (Page 3)

Electrical Information for Standard 24 VDC Excitation Pressure Transducers (nominal)
Connections (Model 204, 239)
Cable Lead
Function Note: Other leads in the cable are not used with
White Positive Excitation the standard pressure transducer unless the
Yellow Positive Output transducer has been wired for Remote Control
Brown Negative Output (see Remote Control Instructions).
Black Negative Excitation - (to circuit ground)
Shield Case
Connections (Model 204, 239) (Grey or White Cable)
Cable Lead
Function
Red Positive Excitation
Black Negative Excitation
White Negative Output
Green Positive Output
Shield Case
Electrical - The electrical circuit is equivalent to a 4 terminal network, which means negative
excitation lead shall not be connected to negative signal output lead.
The pressure transducer must be operated with the case connected to earth ground to meet
EMC requirement. Best performance will be achieved by connecting the shield and negative
excitation lead if it is feasible and allowed.
The circuit has internal protection:
Reversed excitation voltage for at least 5 minutes.
Short-circuit or signal output leads.
Short duration power line transients up to 150 volts.
Note on long cable use:
In some instances, use of long cables (several hundred feet length) may introduce enough cable
capacitance into the circuit to cause output oscillations. If encountered, this oscillation may
be eliminated by connecting a 100 ohm resistor (1/8th watt or larger) in series to each of the
output leads at the end of the 2 foot transducer cable. These series resistors, of course, add to
the output resistance.
Atmospheric Reference (Gauge Pressure Transducers only)
Lower range units are subject to excessive thermal zero shift unless vented to atmosphere. The
electrical cable provides this equalization vent. Do not seal the electrical cable when installing
3
Fixed
Adjustable
6 Remote Control Instructions for Pressure Transducers
Cable leads indicated below are connected into the transducer circuitry on this transducer as ordered.
Connection of the remote control leads extends the internal zero and sensitivity adjustments. The
Transducer was factory calibrated with the remote control wiring disconnected.
CAUTION: The remote control leads directly access active circuit elements. Inadvertent short-circuiting
to each other, to ground, or other miswiring may cause immediate circuit damage. Keep remote control
wiring either free of other contact or else keep the leads properly wired as shown below.
Note: All resistance elements are 0.1 watt or greater. All remote circuits have voltages less than 10
volts and currents less than 1 mA.
Remote Zero Adjustment (standard)
The transducer has been preset with the regular
internal zero adjustment potentiometer. If remote
zero control is desired, connect the orange, green
and black leads as shown with external resistors
and potentiometers.
Remote Sensitivity Adjustment (optional)
The transducer has been preset with the regular
internal sensitivity adjustment potentiometer. If
remote sensitivity control is desired (Option 642),
connect the yellow, blue and violet* leads and
adjustable resistance as shown.
*For Models 239 and 204 w/options 621/622 and
642, replace violet lead as shown.
Remote Calibration Signal (optional)
Two types of calibration signal zero offset are
offered:
Fixed calibration signal closing red to black
leads.
Adjustable calibration signal, on closing circuit
with an adjustable resistance between red and
black leads. Suggest use of a 100K potentiom-
eter.