How should you confirm the function of each pin before wiring an aviation connector pressure transmitter? Knowing the correct verification procedure can help prevent equipment failures caused by incorrect wiring. Before beginning, confirm the specific model, output type, and viewing direction of the connector, then check each pin against the wiring information provided by the manufacturer. Do not rely solely on the number of pins or wire colors.

I. Confirm the product model and wiring information

1. Check the nameplate and the actual product

After disconnecting the power, check the transmitter nameplate and record the product model, supply voltage, output signal, and measurement range. Then check the number of connector pins, the keyway, and the pin numbers to confirm that the wiring diagram applies to the product in question.

Pressure transmitters with the same four-pin aviation connector may have different internal wiring. Even products with similar appearances may have different pin assignments across batches or custom versions. If the nameplate information does not match the documentation, stop before wiring.

Use the supplied manual, product label, factory wiring diagram, or documentation provided by the manufacturer for the specific serial number. If the equipment has been repaired, the connector replaced, or the wiring modified on site, also check the repair records to avoid relying on an obsolete diagram.

2. Confirm the viewing direction shown in the diagram

Aviation connector wiring diagrams usually specify a “pin-end view,” “socket-end view,” or “solder-end view.” The pin arrangement may appear as a mirror image when viewed from the contact face versus the wiring end, so do not apply the diagram without checking.

Align the connector keyway, notch, or locking feature with the diagram, then locate the numbers or letters marked on the insulator. If the markings are small or difficult to read, use a light and magnification.

If the viewing direction is not specified in the diagram, photograph the front, rear, and nameplate of the connector and ask the manufacturer to confirm. Do not apply power as a way of identifying the correct pins.

II. Identify pin functions according to the output type

1. Distinguish between power, signal, and communication pins

Common pressure transmitter outputs include 4–20 mA current, 0–5 V or 0–10 V voltage, and digital communication signals. The terminals required vary by output type; refer to the electrical schematic for the specific model.

Two-wire 4–20 mA products typically use the same two wires for both power and the signal loop. Three-wire products typically have a positive power supply, common, and signal output. The actual terminal names and wiring method must still be confirmed against the manufacturer's documentation.

Products with digital communication or multifunction outputs may have additional communication, switching, or shield terminals. Do not connect undefined pins to the power supply or ground, or short them to other pins.

2. Match function names to pin positions

After confirming the output type, locate the power positive, power negative or common, signal, and other markings on the wiring diagram, then match them to the actual pin numbers on the aviation connector. When recording the assignments, also note the viewing direction for easier verification.

For products supplied with a matching cable, also confirm how the wire colors at the other end correspond to the pins. Wire color is only a secondary identification aid; different manufacturers or replacement cables may use different color schemes.

The shield, metal housing, and signal common are not necessarily electrically connected, and should not be assumed interchangeable. Determine the shielding and grounding method according to the product instructions and the site's electrical design.

III. Measure with the power off and verify the circuit

1. Check the matching cable with a multimeter

With all equipment completely powered off and the connector disconnected from the transmitter, use the continuity setting on a multimeter to check the matching cable: touch one probe to a confirmed socket, then touch the other probe to each cable conductor in turn and record the corresponding connections.

After testing each wire, check for unintended shorts between adjacent conductors and inspect the solder joints, crimp connections, and insulation for looseness or damage. Continuity testing confirms cable connections only; it cannot, by itself, verify the functions of the transmitter's internal pins.

Do not use the continuity setting on an energized circuit, or apply voltage to unknown pins to determine their functions. Before performing insulation or dielectric withstand testing on the transmitter itself, confirm that the test method is permitted by the manufacturer.

2. Check the power supply and receiving equipment

Before wiring, check that the actual power supply output is within the range specified on the nameplate and confirm the DC supply polarity. The input type of the receiving equipment must also match the transmitter; current and voltage inputs must not be interchanged arbitrarily.

For a 4–20 mA loop, for example, in addition to checking the supply voltage, calculate the load from the receiving instrument, wiring, and other components, and ensure that sufficient operating voltage remains at the transmitter. Calculate the permissible load according to the product documentation.

Industrial sites may also use pressure and displacement measurement equipment. For example, China-made PT1A string potentiometer displacement sensor, draw-wire displacement sensor, cable-pull encoder, and gate opening meter can be used to measure positions such as gate openings, with resistance, voltage, and current output options. Its wiring must also be checked against the selected specification; do not apply the pin assignments of a pressure transmitter.

IV. Power up after verification and shut down promptly if an abnormality occurs

1. Perform a final check before powering up

After completing the wiring, verify each pin against the wiring diagram, check that the connector is fully engaged and the locking mechanism is secured, and ensure that the cable seal is reliable. Where the site is damp or subject to washdown, also confirm that the connector and cable assembly meet the required protection rating.

Set the receiving instrument to the correct signal type and range. For example, if the transmitter range is 0–1 MPa, configure the display or control system accordingly. An incorrect range setting can cause inaccurate readings and lead to misjudgment even when the wiring is correct.

After confirming that the pressure connection, medium, and operating pressure meet the equipment requirements, power up in accordance with site procedures. Work involving high pressure, hazardous media, or hazardous areas must be carried out by appropriately qualified personnel in compliance with site safety requirements.

2. Monitor the signal and keep records

Troubleshooting points

After powering up, first check the power supply and receiving instrument status. Then, under safe and controlled conditions, check whether the output changes with pressure. For a linear 4–20 mA output, the lower and upper range limits typically correspond to 4 mA and 20 mA, respectively; always refer to the product instructions.

If there is no signal, the reading is abnormal, communication fails, or the power supply protection is triggered, disconnect the power first, then check the pin positions, polarity, cable continuity, and instrument settings. Do not repeatedly connect or disconnect the connector while powered, or swap wire positions at random.

Record the confirmed model, pin assignments, wire colors, viewing direction, and receiving-end connections in the maintenance documentation. If reliable drawings are not available on site, provide the nameplate, photos of the front and rear of the aviation connector, and the output requirements to the technical team at Xi'an Shenghongchuang Instrumentation Co., Ltd. Confirm the applicable wiring diagram before proceeding.