Setra Systems 256 Installation Manual - Setra Model 256

4

Setra Model 256

Pressure Transducer

1.0 GENERAL INFORMATION

Every Model 256 has been tested and calibrated before shipment.  Specific

performance specifications are listed on Page 7 of this Guide.

Setra Systems 256 pressure transducers sense gage pressure and convert this

pressure to a proportional high level analog output.  Two output versions are

offered:  A voltage output of .1 to 5.1 VDC, and a current output of 4 to 20 mA.

2.0 MECHANICAL INSTALLATION

 2.1 Media Compatibility

Model 256 transducers are designed to be used with any gas or liquid compat-

ible with 17-4 PH Stainless Steel.  (Hydrogen is not recommended for use with

17-4 PH SS.)

 2.2  Environment

 The operating temperature limits of the 256 are as follows:

Operating Temperature Range 

°

F (C

°

) -40 to +260 (-40 to +125)

Compensated Temperature Range

°

F (C

°

)

-4 to +176 (-20 to +80)

 2.3  Pressure Fittings

 Typically, standard pipe fittings and installation procedures should be used.

 However, for very high pressure ranges in excess of 500 psig, we suggest the

 use of a sealant such as Loctite Hydraulic Sealant.  Excessive high torquing of

 metal fittings may cause a slight shift of the output, but this shift can be

 trimmed out by the zero adjustment.  Torquing does not significantly affect

 linearity or sensitivity.

2.4  Moisture Precautions

The Model 256 is provided with two 1/2” NPT female conduit ports for electrical

termination.  These tapered pipe threads are tapped deeper than the NPT

standard, in accordance with industry guidelines.  These ports must be sealed

according to standard industry practice, in order to prevent moisture ingress

into the Model 256.

2.5  Venting

The Model 256 is a true gage pressure transducer.  This means that the

reference side of the pressure sensing diaphragm must be vented to atmo-

sphere.  If the reference side of the diaphragm were sealed (as in a sealed gage

transducer), temperature changes would cause the reference pressure to vary.

This may affect the overall accuracy, especially in ranges lower than 500 psig.

The Model 256 provides a vent from the reference side of the sensor to the

inside of the housing and the conduit ports.  The user-provided electrical

conduit must be vented to atmosphere in a clean dry location.  (It is important

to prevent moisture ingress from the environment into the wiring chamber

or reference side of the transducer.)