ASHCROFT A2 Industrial Pressure Transmitter Instructions

ASHCROFT A2 Industrial Pressure Transmitter

A2 Pressure Transmitter

The A2 Pressure Transmitter is a device used for measuring pressure in industrial applications. It is designed to withstand normal vibration without damage or significant output effects. However, it is recommended that the device be mounted in a location with minimum vibration. The device comes in different enclosure options (S, Z, and W) and cable or conduit-style electrical termination.

Product Usage Instructions

1. Before installation, read the user manual carefully and contact Ashcroft Inc., Stratford, Connecticut, USA if you have an questions or concerns.
2. Avoid excessive overpressure, excessive vibration or pressure pulsation, excessive instrument temperature, corrosion of the pressure-containing parts, or another misuse. Install a pressure snubber to eliminate damaging hammer effects caused by fluid hammer and surges. Symptoms of fluid hammer and surge’s damaging effects include freezing of media in the pressure port.
3. Avoid exposing the device to static electrical charges. The shield and drain wire in the cable (if supplied) is not connected to the transducer body and is not a suitable ground.
4. The A2 transmitter requires no special mounting hardware and can be mounted in any plane with negligible position error. When tightening, apply a wrench to the hex wrench flats located just above the pressure fitting. DO NOT tighten by using a pipe wrench on the housing.
5. The power supply voltage range is 0-10VDC and the output signal range is 0-5Vdc, 1-5Vdc, 1-6Vdc, 0-10V, or 4-20mA.

BEFORE INSTALLATION

1. GENERAL:
   A failure resulting in injury or damage may be caused by excessive overpressure, excessive vibration or pressure pulsation, excessive instrument temperature, corrosion of the pressure-containing parts, or another misuse. Consult Ashcroft Inc., Stratford, Connecticut, USA before installing if there are any questions or concerns.

2. OVERPRESSURE:
   Pressure spikes in excess of the rated overpressure capability of the transducer may cause irreversible electrical and/or mechanical damage to the pressure measuring and containing elements.
   Fluid hammers and surges can destroy any pressure transducer and must always be avoided. A pressure snubber should be installed to eliminate the damaging hammer effects. Fluid hammer occurs when a liquid flow is suddenly stopped, as with quick closing solenoid valves. Surges occur when flow is suddenly begun, as when a pump is turned on at full power or a valve is quickly opened.

Liquid surges are particularly damaging to pressure transducers if the pipe is originally empty. To avoid damaging surges, fluid lines should remain full (if possible), pumps should be brought up to power slowly, and valves opened slowly. To avoid damage from both fluid hammer and surges, a surge chamber should be installed.
Symptoms of fluid hammer and surge’s damaging effects:

• The pressure transducer exhibits an out-put at zero pressure (large zero offsets).
• Pressure transducer output remains constant regardless of the pressure
• In severe cases, there will be no output.

FREEZING:
Prohibit freezing of media in pressure port. The unit should be drained (mounted in a vertical position with electrical termination upward) to prevent possible over-pressure damage from frozen media.

STATIC ELECTRICAL CHARGES:

Any electrical device may be susceptible to damage when exposed to static electrical charges. To avoid damage to the transducer observe the following:

• The operator/installer should follow the proper ESD (electrostatic discharge) protection procedures before handling the pressure transducer.
• Ground the body of the transducer BEFORE making any electrical connections
• When disconnecting, remove the ground LAST!
  Note: The shield and drain wire in the cable (if supplied) is not connected to the transducer body, and is not a suit-able ground.

Dimensions

*Ashcroft® A2 Pressure Transmitter, Typical Dimensions and Construction**

Mounting

The A2 transmitter requires no special mounting hardware, and can be mounted in any plane with negligible position error.
Although the unit can withstand normal vibration without damage or significant output effects, it is always good practice to mount the transducer where there is minimum vibration.
For units with NPT type pressure fittings apply Teflon® tape or an equivalent sealant to the threads before installing.
When tightening, apply a wrench to the hex wrench flats located just above the pressure fitting. DO NOT tighten by using a pipe wrench on the housing.

Power Supply

• For transmitters with 4-20mA output signal, the minimum voltage at the termi-nals is 12Vdc. However, the minimum supply voltage should be calculated

Loop Supply Voltage vs. Loop Resistance

Vmin = 12V+ (.022A x RL) (includes a 10% safety factor) RL = RS + RW
RL = Loop Resistance (ohms)
RS = Sense Resistance (ohms)
RW = Wire Resistance (ohms)

Noise
For minimum noise susceptibility, avoid running the transducer’s cable in a conduit that contains high-current AC power cables. Where possible avoid running the cable near inductive equipment.

Shielded Cable
Units with shielded cable electrical termination, connect the drain wire to the guard terminal on the read-out device or measuring instrument, if available. In all other cases connected to the ground or to the power supply negative terminal.

Sintered Metal Filter
All units less than 500 psi include a small metal sintered filter at the top of the unit. This is necessary to equalize the internal pressure with atmospheric pressure but can be a point of moisture ingress.

A2 Wiring Diagrams

A2 transducer has internal transient protection: for safety, limit line-to- ground voltage to 36 Vdc max.

Zero and Span Adjustment

Instructions below apply to the particular configurations noted, not all A2 configurations offer Zero and Span access. While Zero adjustment is not normally necessary, it may be desirable to trim out any offset in the system. However, proper Span calibration requires a pressure standard three to five times more accurate than the accuracy of the transducer, and there may also be the interaction of Span on Zero.

1. Side access zero and span adjustment
   (Enclosure Options “Z,” “Y”) A2 configurations with side access “Z” and “S” potentiometers (pots) have a black plastic access sleeve towards the electrical termination end of the unit (see diagram on front page).
   To gain access to the zero and span adjustment pots, slide the access sleeve upward toward the connector. On the label there is a “Z” and “S” to indicate zero and span. (Looking at the A2 vertically as in the diagram, zero is on the left and the span is on the right). Using a small trim pot adjustment tool you can adjust zero ±10% of full scale and span ±10% of full scale.

2. Top/rear access zero and span adjustment
   Access to “Z” and “S” pots via the top (electrical termination end) of the unit is standard on all “S” enclosure units with 4-20mA output. Access is gained by removing the black threaded cap, once removed you will see the pots indicated by “Z” and “S” respectively as shown below. Using a small trim pot tool, you can adjust zero±10% of full scale and span ±10% of full scale.

Recalibration Instructions:

1. Apply 0% full-scale pressure.
2. Adjust the output using the zero-adjust trim pot.
3. Apply 100% full-scale pressure.
4. Adjust the output using the span adjustment trim pot.
5. Repeat steps 1 through 4 as necessary.

A2 PRESSURE TRANSMITTER INSTRUCTION SHEET

ELECTRICAL TERMINATIONS FOR WELDED HOUSINGS ONLY Visit our web site www.ashcroft.com

Ashcroft Inc.
250 East Main Street
Stratford, CT 06614-5145 USA
Tel: 203-378-8281 • Fax: 203-385-0402 email: info@ashcroft.com
www.ashcroft.com

References

• Pressure Instruments - Temperature Instruments | Ashcroft

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