Setra 270 Operating Manual

Operating Instructions

Model 270 Pressure Transducer

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. Pressure range and dimensions are reported on the
specifications bulletin for the transducer.

Ambient Conditions

Do not use in ambient conditions corrosive to anodized aluminum, or submerge in liquids, subject to spray
or vibration environment.

Electrical Connections:

Standard

“Belden” Cable Lead Optional
Function (#8723 Grey Cable) “Tensolite” Cable Lead
Positive Excitation Red White
Positive Output Green Yellow
Negative Output White Brown
Negative Excitation Black Black
Case Shield Shield

Electrical

The electrical circuit is equivalent to a 4-terminal network which can be grounded at only one point, either
at the negative excitation or the negative signal output lead, but must not be commoned or grounded at
more than one point.

The pressure transducer must be operated with the case connected either to the negative excitation
terminal or to the negative output terminal. Failure to do this may result in damage to, or unsatisfactory
operation of the unit. This connection may be made by connecting shield and black (negative excitation)
leads or alternatively by connecting the shield and negative output signal leads together. Best shielding
against noise will be obtained by connecting the shield and negative excitation leads. Circuit is reversed
voltage protected for at least 5 minutes. Internal transient suppression network is provided for short
duration transients to 150 volts.

In some instances, use of long cables (several hundred feet long) , may introduce enough cable capaci­tance 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 in each of the output leads at the end of the
2 foot transducer cable. These series resistors of course add to the output resistance.

Adjustments (with cover removed)

CAUTIONS: 1. Before making any adjustments, determine which circuit board diagram on

Page 2 matches the circuit board in your transducer.

2. Turn off excitation power during cover removal or replacement.

3. Touching any adjustments other than zero or span may necessitate
recalibration and voids the warranty.

ZERO OUTPUT

Output can be adjusted to zero by potentiometer as shown in diagram. Unit factory adjusted to

0.00 VDC output (±5mV).

SPAN

Can be adjusted by potentiometer as shown in diagram. Unit factory adjusted to 5.00 VDC full
scale output (±5mV).

LINEARITY - DO NOT TOUCH

Factory adjusted for best linearity.

Circuit Board 1 Circuit Board 2

NOTE: When circuit cover is removed, a zero shift can be noticed. The zero will return by the same
amount when the cover is replaced. This displacement of the output should be taken into account when
making adjustments or during recalibration

*Adjustments: Due to the high accuracy of this transducer, adjustments to zero and span should only be
made with the use of primary pressure standards of known accuracy higher than that of the Model 270.