HM SERIES — PIEZORESISTIVE TECHNOLOGY
HM20 General Purpose Pressure Transmitter
The HM20 is our most versatile pressure transmitter — designed for engineers who need reliable, accurate pressure measurement across the broadest range of industrial and OEM applications. Co-developed with Germany’s HMK company, the HM20 combines an imported diffused silicon sensing element with standardized signal conditioning, delivering ±0.25% FS accuracy from vacuum to 100 MPa in a compact, field-proven package.
±0.25% FS Accuracy5 kPa – 100 MPa4-20mA / 0-5V / 0.5-4.5VIP67Ex ia (Optional)
Why the HM20 Is Our Best-Selling Industrial Transmitter
When we set out to design the HM20, the goal was straightforward: build a pressure transmitter that works reliably in 90% of industrial applications without requiring special configuration or exotic materials. That meant wide operating temperature range (-40 to 85°C), solid vibration resistance (≤±0.01% FS at 200 Hz/g), and a response time under 2 milliseconds — fast enough for real-time process control loops.
The sensing element is a German-imported piezoresistive silicon chip, laser-trimmed for temperature compensation across the full -10 to 60°C compensated range. Each unit undergoes individual calibration before leaving our facility, and every transmitter ships with a traceable calibration certificate.
The HM20 accepts gauge or absolute pressure, outputs 4-20mA (two-wire), 1-5V, 0-5V, or 0.5-4.5V, and connects through M20×1.5, G1/4, 1/4 NPT, or custom process fittings. That flexibility makes it equally at home on a compressor test stand, a hydraulic press, a water treatment pump station, or an HVAC chiller loop. Wondering whether your application actually needs a transmitter instead of a raw sensor? See our pressure sensor vs transmitter selection guide.
For hazardous area installations, the HM20 is available with intrinsically safe certification (Ex ia II CT5) — just add the “E” option code when ordering and power through an approved safety barrier.
HM20 Technical Specifications
| Parameter | Specification |
|---|---|
| Sensing Technology | Piezoresistive diffused silicon (German HMK import) |
| Measurement Range | -100 kPa to 0 … 5 kPa to 100 MPa (vacuum to 14,500 psi) |
| Pressure Type | Gauge (G) or Absolute (A) |
| Comprehensive Accuracy | ±0.25% FS (standard) | ±0.4% FS (economy) |
| Long-term Stability | Typical: ±0.1% FS/year | Max: ±0.2% FS/year |
| Overload Pressure | 2× full-scale (1.1× for 100 MPa models) |
| Output Signal | 4-20mA (two-wire) | 1-5V DC | 0-5V DC | 0.5-4.5V DC |
| Power Supply | 12–36 V DC (24 V DC typical) |
| Load Resistance | ≤ (Vsupply − 12) / 0.02 Ω — e.g. 600 Ω at 24 V DC |
| Response Time | ≤ 2 ms |
| Operating Temperature | -40 to +85°C (-40 to +185°F) |
| Compensated Temperature | -10 to +60°C (14 to 140°F) |
| Zero / Span Temp Drift | Typical: ±0.02% FS/°C | Max: ±0.05% FS/°C |
| Vibration Resistance | ≤ ±0.01% FS (X, Y, Z axes at 200 Hz / 1g) |
| EMC / RF Immunity | EN 50081-1, EN 50082-2, IEC 61000-4-3 |
| Wetted Material — Diaphragm | 316L Stainless Steel |
| Wetted Material — Housing | 1Cr18Ni9Ti Stainless Steel (≈ AISI 321) |
| Wetted Material — O-Ring | FKM (Viton) fluorocarbon rubber |
| Process Connection | M20×1.5 | G1/4 | 1/4 NPT | 1/2-20 UNF | Custom |
| Electrical Connection | DIN 43650 connector (IP65) | Cable gland (IP67) |
| Protection Grade | IP65 (connector) | IP67 (cable) |
| Explosion Protection | Ex ia II CT5 (optional, order code “E”) |
| Weight | Approximately 500 g (1.1 lb) |
| Certifications | CE | RoHS | Ex ia II CT5 (optional) |
Key Features & Engineering Benefits
🔬 German-Imported Silicon Sensing Element
The core piezoresistive chip is manufactured by HMK (Germany), laser-trimmed for linearity and temperature compensation. This delivers consistent accuracy across units — critical for OEM customers ordering in volume where unit-to-unit variation must be minimized.
📡 Multiple Output Signals, One Platform
Choose 4-20mA (industry standard for long cable runs up to 1,500 m), 0-5V (common in PLCs and data loggers), 1-5V, or 0.5-4.5V (ratiometric, common in automotive and mobile hydraulics). Same sensing platform, same accuracy — just specify the output code when ordering.
🌡️ Wide Operating Temperature: -40 to +85°C
The compensated range extends from -10 to 60°C, covering the majority of indoor and outdoor industrial environments. The extended operating range (-40 to 85°C) handles cold-start conditions in northern climates and elevated ambient temperatures near engines, compressors, and boilers.
🛡️ Robust Construction for Harsh Environments
All-stainless-steel wetted parts (316L diaphragm, 1Cr18Ni9Ti housing), FKM O-ring seals, IP67 protection (cable type), and vibration resistance certified to 200 Hz/1g. The HM20 handles the mechanical stress of pumps, compressors, and mobile equipment without signal degradation.
⚡ Fast 2 ms Response Time
A ≤2 ms response time means the HM20 captures pressure transients that slower transmitters miss. This matters in applications like compressor surge detection, hydraulic system monitoring, and process control loops where delayed readings translate to delayed corrective action.
🔧 Fully Configurable for OEM Integration
The HM20’s modular design supports custom pressure ranges, process connections, electrical connections, cable lengths, and output signals. For OEM customers, we also offer custom labeling, special calibration ranges, and modified housing dimensions. Minimum order quantities for custom configurations are reasonable — we support both prototype and production runs.
Industrial Applications for the HM20
The “general purpose” designation means exactly what it says — this transmitter handles an unusually broad range of process conditions. Here are the applications where the HM20 is most commonly deployed:
Hydraulic & Pneumatic Systems
The HM20’s 100 MPa maximum range covers the full spectrum of industrial hydraulic pressures. The 2 ms response time captures pressure spikes that can indicate pump cavitation, seal failures, or valve malfunction. For mobile hydraulics, the 0.5-4.5V ratiometric output interfaces directly with ECU analog inputs.
Water Treatment & Pump Stations
Municipal and industrial water systems rely on accurate, stable pressure measurement for pump control, filter monitoring, and distribution management. The HM20’s ±0.1% FS/year long-term stability means fewer recalibration cycles, and the 4-20mA output runs over standard instrumentation cable to SCADA PLCs up to 1,500 m away.
HVAC & Refrigeration
Chiller systems, heat pumps, and commercial refrigeration units need reliable suction and discharge pressure monitoring for compressor protection and energy optimization. The HM20 covers refrigerant pressures from low-side vacuum through high-side discharge, and the -40°C minimum operating temperature handles cold-start scenarios.
OEM Equipment Integration
Equipment manufacturers choose the HM20 for its combination of performance and value. When embedding 50 or 500 transmitters per month into compressors, test stands, or process skids, consistent calibration accuracy from unit to unit matters more than the last digit of precision.
Test Stands & Laboratory
Automotive test cells, hydraulic component test benches, and quality control stations use the HM20 for its fast response and wide range selection. The ±0.25% FS accuracy meets most production testing protocols, and the compact form factor fits into space-constrained test fixtures.
Agricultural & Irrigation Systems
Pivot irrigation controllers, fertigation systems, and agricultural sprayer equipment use the HM20 to monitor line pressure and detect nozzle blockages or pipe bursts. The rugged construction withstands mechanical vibration of tractor-mounted equipment, and the 0.5-4.5V output interfaces directly with agricultural controller modules.
HM20 Model Selection & Ordering Guide
Build your HM20 model code by selecting options from each column below. Not sure which configuration you need? Contact our engineering team — we’ll review your application and recommend the right setup.
Model Code Structure: HM20 (Range) — Accuracy — Output — Connection — Options
| Selection | Code | Description |
|---|---|---|
| Pressure Type | ||
| Gauge Pressure | G (or omit) | Referenced to atmospheric pressure |
| Absolute Pressure | A | Referenced to vacuum (sealed reference) |
| Accuracy | ||
| ±0.4% FS | 1 | Standard accuracy |
| ±0.25% FS | 2 | High accuracy (recommended) |
| Output Signal | ||
| 4-20 mA (two-wire) | A1 | Industry standard, long cable runs, noise immune |
| 1-5 V DC | V1 | Three-wire, common in PLCs |
| 0-5 V DC | V2 | Three-wire, common in data loggers |
| 0.5-4.5 V DC | V3 | Ratiometric, common in automotive/mobile |
| Process Connection | ||
| M20×1.5 male | F1 | Metric standard |
| G1/4 male (BSP) | F2 | British standard pipe |
| 1/4 NPT male | F3 | North American standard |
| 1/2-20 UNF-2A | F4 | SAE / hydraulic fitting |
| Electrical Connection | ||
| Cable gland (IP67) | W1 | Direct cable exit, best environmental sealing |
| DIN 43650 connector (IP65) | W2 | Field-replaceable, industry standard |
| Options | ||
| LCD Display (3½ digit) | L1 | Local pressure readout |
| LED Display (3½ digit) | L2 | Local readout, visible in low light |
| Flush Diaphragm | P | For viscous or crystallizing media |
| Intrinsically Safe | E | Ex ia II CT5 — requires safety barrier |
Example Order Code: HM20 (0–100 kPa) — 2 — A1 — F3 — W2
HM20, 0–100 kPa gauge, ±0.25% FS accuracy, 4-20mA output, 1/4 NPT, DIN 43650 connector.
HM20 Dimensions & Mounting
The HM20 mounts directly into a pressure port via its threaded process connection. No additional brackets or mounting hardware required. For panel or pipe mounting, optional mounting brackets are available — specify when ordering.
Installation Notes
- Apply thread sealant tape (PTFE) to male thread connections. Do not use liquid pipe compound on the first two threads to avoid contaminating the sensing diaphragm.
- Tighten to recommended torque: 15–25 N·m for M20×1.5 and G1/4 connections. Use a wrench on the hex flats only — never tighten by gripping the transmitter body.
- For pulsating pressure applications, install a snubber or needle valve upstream of the transmitter to dampen pressure spikes that exceed the 2× overload rating.
- Mount vertically with the process connection pointing down when measuring liquids, to allow trapped air to vent back into the process line.
- For steam or high-temperature media (>85°C), use a siphon tube or cooling element to keep the transmitter within the -40 to 85°C operating range.
Related Pressure Transmitters
HM20 Frequently Asked Questions
Ready to Order the HM20?
Tell us about your pressure measurement requirements — including media type, pressure range, process connection, and output signal. Our engineering team will recommend the optimal HM20 configuration for your specific application.
Typical lead time: 5–7 business days. Volume discounts available for OEM orders.