Follow this 5-step selection sequence
Work through these five decisions in order. If you are unsure at any step, stop and ask the supplier rather than skipping ahead on experience.
- 1. Medium and pressure type — What are you measuring (water, air, hydraulic oil, corrosive media)? Do you need gauge, absolute, or sealed gauge pressure?
- 2. Range — Size so the normal operating point falls between 30% and 70% of full scale. For pump and hydraulic circuits, confirm overpressure protection of at least 2x full scale; do not rely on the nameplate range alone.
- 3. Signal and power — If the reading must reach a PLC or DCS, take the transmitter path (4-20mA 2-wire loop is the default; RS485 Modbus for multi-point runs). If you only need a local reading, consider the digital gauge path. Confirm whether your panel provides loop power (typically 12-36V DC).
- 4. Connection and wetted materials — Confirm the thread standard your fitting stock uses (G1/4, G1/2 for general industry; NPT for North American projects) before ordering. For corrosive media specify 316L wetted parts or a diaphragm seal; for viscous, crystallizing, or sanitary media use a flush diaphragm.
- 5. Environment and certification — For oil and gas, chemical, or dusty environments, send the area classification and required protection type to the supplier first, and ask for the current certificate: check holder, model scope, marking, issuer, and validity. Do not infer coverage from a category-page label.
Prepare these inputs before you request a quote
A buyer who fills in this checklist gets an accurate model confirmation in one round instead of three.
- Pressure type — gauge, absolute, or sealed gauge.
- Normal operating pressure — keep the working point within 30-70% of the selected range.
- Surge and water hammer — any pump starts or fast valve closures? Water hammer can spike to 3-5x operating pressure for milliseconds; require at least 2x full-scale overpressure protection.
- Accuracy class — 0.5% FS covers general monitoring; 0.25% FS suits process control loops; 0.1% FS is for test benches and calibration references. Also check long-term stability (%FS/year) and compensated temperature range.
- Output signal — 4-20mA 2-wire loop is the industrial default (wire-break detectable); RS485 for multi-point runs; 0-10V degrades over long cable runs.
- Power — 12-36V DC typical; confirm whether the panel provides loop power.
- Process connection — G1/4, G1/2, NPT, M20, flange, diaphragm seal, or sanitary; match your spare-parts stock before ordering.
- Wetted materials — standard 304 for water, air, and hydraulic oil; 316L or diaphragm seal for corrosive media; flush diaphragm for viscous or crystallizing media.
- Environment — outdoor (IP65 minimum, IP67 for hose-down), hazardous area (area classification plus protection type required), high vibration (send measured vibration data, not a generic description).
- Certification documents — request the current certificate and verify holder, model scope, marking, issuer, and validity. Until the certificate scope is confirmed, do not accept hazardous-area coverage claims.
- Accompanying documents — individual traceable calibration certificate, material certificates, manual; EPC handovers routinely require the full package.
- Remote vs local reading — need a PLC signal? Take the AM-PT300 transmitter path. Need a local digital display, battery power, or private labeling? Take the AM-PG200 digital gauge path.
- Model-specific parameters — check the published specifications on the AM-PT300 and AM-PG200 product pages; the exact datasheet for the quoted model is confirmed with the quotation.
Choose range with overpressure margin, not nameplate pressure
Size the transmitter so normal operating pressure sits between 30% and 70% of full scale. This preserves accuracy at the working point and leaves headroom for transients. Water hammer in pump systems can spike to 3-5x operating pressure for milliseconds — check the transmitter's overpressure rating, not just its range.
For hydraulic systems running 20 MPa, a 0-40 MPa transmitter with 2x overpressure protection is a safer choice than a 0-25 MPa unit at the edge of its band.
- Operating point: keep within 30-70% of the selected range.
- Overpressure rating: at least 2x full scale for pump and hydraulic circuits.
- Burst pressure: verify separately for safety-critical installations.
Match accuracy class to the application
0.5% FS accuracy covers most monitoring and control tasks at the lowest cost. 0.25% FS suits process control loops where the PLC acts on small pressure changes. 0.1% FS is for test benches, calibration references, and custody-adjacent measurement — paying for it on a simple tank monitoring point is wasted budget.
Also check long-term stability (percent of FS per year) and the compensated temperature range. A transmitter accurate at 25°C but uncompensated at your process temperature will drift in the field.
Output signal and wiring
4-20mA 2-wire loop-powered remains the default for industrial installations: simple, noise-resistant, and detects wire breaks (current drops below 4mA). RS485 Modbus suits multi-point monitoring on one cable run. 0-10V is common in HVAC but degrades over long cable distances.
Confirm supply voltage range (12-36V DC typical) and whether your panel provides loop power or the transmitter needs a separate supply.
Process connection and wetted materials
G1/4 and G1/2 threads dominate general industry; NPT is standard for North American projects — confirm which one your fitting stock uses before ordering 200 units with the wrong thread. For corrosive media, specify 316L stainless steel wetted parts or a diaphragm seal; standard 304 housings handle water, air, and hydraulic oil.
For viscous, crystallizing, or sanitary media, a flush diaphragm connection prevents clogging of the pressure port.
Certification for the installation environment
For oil and gas, chemical, and dust-explosion environments, specify ATEX or IECEx explosion-proof certification (e.g. Ex d IIC T6) and verify the certificate names the transmitter model. For outdoor installations, IP65 is the minimum; IP67 where hose-down or temporary flooding is possible.
Every unit should ship with an individual calibration certificate traceable to reference standards — this is standard practice from ISO 9001 certified factories and required documentation for many EPC project handovers.
Six common selection mistakes
Most mis-specifications come from the same handful of oversights. None of them require a named customer to learn from.
- Sizing by nameplate range alone, ignoring overpressure — water hammer at 3-5x operating pressure is a millisecond event; without 2x overpressure protection, early failure in pump systems is the most common cause.
- Buying 0.1% accuracy for a trend-monitoring point — 0.5% FS is enough; the extra money buys no usable information.
- Running 0-10V over long cable distances — voltage signals attenuate with cable length; use a 4-20mA current loop or RS485 instead.
- Mixing NPT and G threads on one order — North American projects default to NPT, general industry to G1/4 and G1/2; confirm your fitting stock before ordering 200 units, because a wrong batch means full rework.
- Treating IP65 as explosion protection — ingress rating and hazardous-area protection are two different systems; hazardous-area selection starts with the area classification and a verified certificate.
- Comparing price without comparing the document package — EPC handover needs calibration certificates, material certificates, and manuals; the cheapest quote with incomplete documents stalls at site acceptance.
OEM/ODM: what to prepare
For private-label and custom projects, prepare these inputs with the inquiry. Commercial terms are confirmed during project quotation, not at the selection stage.
- Inquiry inputs: label artwork, packaging requirements, range, display, required documents, first-order quantity, and annual volume.
- Confirmed after engineering review: labeling feasibility, tooling, costs, MOQ, validation process, and schedule — each itemized in the project quotation.
- Documents first: for OEM projects, lock in pressure, process, connection, branding, documents, samples, validation, and mass-production release criteria before comparing prices, so prototypes and production do not diverge.
- What is not committed at this stage: hazardous-area coverage before the certificate scope is confirmed, and fixed model parameters where the public datasheet is not yet published.
Related Guides & Applications
Pressure Transmitters for OEM Equipment
Define range, connection, output, housing, branding, documentation, and annual volume for OEM projects.
Read guidePressure Sensor Category
Compare AM-PT300 and AM-PG200 by signal, display, power, certification, and OEM requirements.
Read guideAM-PT300 Pressure Transmitter
Review the published model specs and request a factory quote.
Read guideBuyer FAQ
What accuracy do I need for a pressure transmitter?
0.5% FS is sufficient for general monitoring, 0.25% FS for process control loops, and 0.1% FS for test benches and reference measurement. Higher accuracy costs more and adds no value if the application only needs trend monitoring.
Why does my pressure transmitter fail early in a pump system?
The most common cause is water hammer: pressure spikes of 3-5x operating pressure when valves close quickly. Select a transmitter with at least 2x overpressure rating, keep the operating point below 70% of full scale, or add a pressure snubber.
What is the difference between 2-wire and 4-wire pressure transmitters?
A 2-wire transmitter is loop-powered: the same pair of wires carries both power and the 4-20mA signal, which simplifies wiring. A 4-wire unit has separate power and signal lines, used when the output is voltage or when the sensor needs more power than a loop provides.
Can one pressure transmitter measure 100 MPa?
Yes. High-pressure piezoresistive transmitters cover ranges up to 100 MPa for hydraulic, test-bench, and high-pressure processing applications. Verify the overpressure and burst ratings, and use appropriate high-pressure fittings rated for the same class.
What is the MOQ for OEM or private-label pressure transmitters?
It depends on the model, artwork, packaging, tooling, testing, documentation, and customization scope, and is confirmed in the project quotation after engineering review.
How do I verify a certificate for hazardous-area transmitters?
Send the area classification and required protection type first. Ask the supplier for the current certificate and check five items: holder, model scope, marking, issuer, and validity. Never infer coverage from a category-page label.
For a hydraulic system, should I choose the AM-PT300 or the AM-PG200?
If the reading must reach a PLC or DCS, take the AM-PT300 transmitter path — and send the range, process connection, output signal, and measured vibration data for review. If you need a local digital reading, consider the AM-PG200 gauge path.
Does each transmitter ship with a calibration certificate?
Each unit should ship with an individual calibration certificate traceable to reference standards — standard practice from ISO 9001 factories and routinely required for EPC project handovers.
Validate the model for your project
Review the AM-PT300 specifications against your application inputs, or send the project details for an engineer review and current model-specific documentation.