Setra 205 Operating Manual

OPERATING INSTRUCTIONS

MODEL 205-2 PRESSURE TRANSDUCER

FOUR-WIRE, VOLTAGE OUTPUT

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 ranges and dimensions are reported on the specification bulletin for the transducer.

INSTALLATION

Do not use in ambient conditions corrosive to polyvinyl chloride (cable) or stainless steel, submerged in liquids, subject to spray or drip, or in a high vibration environment. The 205-2 Series is very slightly sensitive to acceleration in the pressure fitting axis, less than 0.05 psi/g typical. Factory calibrated in the vertical position, with pressure port downward, this position often minimizes damage from dripping of pressure system piping.

Installation of pressure fitting:

For very high pressure use of sealant such as Loctite hydraulic sealant is suggested. For other pressure ranges, standard sealants such as Teflon tape generally are satisfactory. For the most sensitive pressure ranges, excessive high torquing of a metal pressure fitting may cause a slight zero shift which may be trimmed out using the zero adjustment. Use of plastic fittings often shows no noticeable zero shift. The torquing effect does not appreciably affect linearity or sensitivity. Use the wrench flats on the 205-2 when attaching to fittings. Installation with FM approved Explosionproof/Weatherproof enclosure:

1. Conduit seals shall be placed no more than 18" from the enclosure.

2. Cables with gas/vapor tight continuous sheath, capable of transmitting gas or vapor through the cable core, shall be sealed per National Electric Code (NEC) for Class 1, Division 1 (most current revision).

3. Caution: Do Not open cover while circuits are live.

ATMOSPHERIC REFERENCE (Gage pressure transducers only)

Lower range units are subject to excessive thermal zero shift unless vented to atmosphere. The electrical cable provides this equalization vent. ELECTRICAL CONNECTIONS:

CABLE LEAD FUNCTION Red positive excitation Green positive output White negative output Black negative excitation Shield case

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 output lead, but must not be commoned or grounded at more than one point. The negative output lead is approximately 1.66 VDC above the negative excitation lead. The positive output lead is at this same 1.66 VDC common mode voltage plus the output signal from applied pressure (thus goes from approximately 1.66 VDC up to 6.66 VDC above the negative excitation).

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 the shield to white or shield to black leads. Best shielding against noise will be obtained by connecting the shield and negative excitation (black) leads.

Linearity Adjust (Do Not Touch)

Sensitivity Adjust

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

Zero Adjust

length) 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.

CAUTION: Excitation power, or voltage in excess of 15 VDC, inadvertently applied to the output leads may damage the electrical circuit. Care must be taken when installing this transducer that the excitation voltage is not applied to the output leads by mistake. Shielding or other precaution should be provided to assure that transient voltages in excess of 15 VDC are not applied to the output leads.

ADJUSTMENTS (with cover removed)

CAUTION: TURN OFF EXCITATION POWER DURING COVER REMOVAL OR REPLACEMENT.

ZERO PRESSURE OUTPUT

Unit factory adjusted to within ± 50 mV. Can be adjusted by the air trim capacitor as shown in the diagram. Any adjustments will begin to change sensitivity.

SENSITIVITY

Can be adjusted by potentiometer as shown on diagram. Unit factory adjusted to order specifications.

OTHER ADJUSTMENT

Adjusted at factory. Touching any adjustments other than zero output or sensitivity may necessitate recalibration. Do not touch.

INSTALLATION INSTRUCTIONS FOR MULTIPLE HOOK UP OF A 4-WIRE SETRA PRESSURE TRANSDUCER

POWER

SUPPLY

GROUND

+EX

-EX

+EX

-EX

+EX

-EX

+out

-out +out

-out

Option#2 Uses a separate, isolated power supply for each pressure transducer's excitation and a single, ground referenced readout or "single-ended input" to a data acquisition system for all of the outputs.

PS - Power Supply (Nominal 24 VDC) PT - Pressure Transducer (4 Wire Circuit) DVM/DAS - Digital Volt Meter or Data Acquisition System

+out

-out

+out

-out

+out

-out

POWER SUPPLY

+EX

-EX

+EX

-EX

+EX

-EX

DVM/DAS

Option #1 Uses a single, ground referenced power supply for excitation and separate, isolated, (not ground referenced), readout or "differential input" to a data acquisition system for each pressure transducer output.

POWER SUPPLY

+EX

-EX

+EX

-EX

+EX

-EX

+out

-out

+out

-out

DVM/DAS

+out

-out

Option #3 Uses a single, ground referenced power supply for excitation and either a single, isolated readout with a bipolar switch that "breaks before makes" both the + output and - output of each pressure transducer, or a single data acquisition system with a multiplexer (MUX).

NOTE: The shield is internally commoned to the case and pressure port of the transducer. When the shield is connected to ground, the case and pressure port of the transducer will also be commoned to that ground.

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