HM SERIES — PIEZORESISTIVE TECHNOLOGY
HM25 Industrial Pressure Transmitter
Piezoresistive silicon sensor with field-mount stainless steel housing, HART protocol, and ±0.1% FS accuracy — engineered for process plants requiring local display, wide temperature range, and drop-in replacement compatibility.
100 MPaMax Range±0.1%AccuracyHARTProtocolIP65Protection
Built for Process Plants: From Control Room to Field
In a petroleum refinery, pharmaceutical clean room, or power plant boiler house, the pressure transmitter needs to do more than output a signal. Maintenance technicians need local readout during rounds. Instrument engineers need HART communication for remote configuration. And the housing needs to survive years of UV exposure, rain, dust, and temperature cycling.
The HM25 addresses all of these with a field-mount stainless steel housing incorporating a dedicated terminal block for clean field wiring, shielded cable entry for EMI rejection, and optional pointer or LCD/LED display for local indication.
Compared to the HM20, the HM25 steps up accuracy to ±0.1% FS, extends operating temperature to -40 to 125°C, and adds HART protocol. The wider compensated range (-20 to 80°C vs. -10 to 60°C) means tighter accuracy in outdoor installations.
Every unit is individually laser-compensated and calibrated against traceable pressure standards. Power supply reverse polarity and overvoltage protection are built in — because in the field, wiring mistakes happen.
HM25 Technical Specifications
| Parameter | Specification |
|---|---|
| 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 | ±0.1% FS | ±0.25% FS | ±0.4% FS (selectable) |
| Long-term Stability | Typical: ±0.1% FS/year | Maximum: ±0.2% FS/year |
| Overload Pressure | 2× full-scale (1.1× for 100 MPa models) |
| Output Signal | 4-20mA | 1-5V | 0-5V | 0.5-4.5V | 4-20mA + HART |
| Power Supply | 12–36 V DC (24 V DC typical) |
| Load Resistance | ≤ (Vsupply − 12) / 0.02 Ω |
| Response Time | ≤ 2 ms |
| Resolution | Infinite (analog) | 1/100,000 of FS typical |
| Operating Temperature | -40 to +125°C (-40 to +257°F) |
| Compensated Temperature | -20 to +80°C (-4 to +176°F) |
| Zero Temperature Drift | Typical: ±0.02% FS/°C | Max: ±0.05% FS/°C |
| Span Temperature Drift | Typical: ±0.02% FS/°C | Max: ±0.05% FS/°C |
| Vibration Resistance | ≤ ±0.01% FS (X, Y, Z 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 | Custom |
| Electrical Connection | φ8 mm cable gland entry on field housing |
| Protection Grade | IP65 |
| Explosion Protection | Ex ia II CT5 (optional, order code “E”) |
| Display Options | None | Pointer (0-100%) | 3½ digit LCD | 3½ digit LED |
| Weight | Approximately 500 g (1.1 lb) |
| Certifications | CE | RoHS | Ex ia II CT5 (optional) |
Key Features & Engineering Benefits
HART Protocol Communication
HART option superimposes digital communication on 4-20mA — no additional wiring. Remotely configure range, damping, read diagnostics, and perform zero/span adjustments. Cuts commissioning time in half on large installations.
±0.1% FS Accuracy Option
Comprehensive accuracy (linearity + repeatability + hysteresis). For 0-10 bar range: ±0.01 bar (±0.15 psi). Satisfies custody transfer metering, fiscal flow measurement, and high-value chemical batch processes.
Local Display: Pointer or Digital
Mechanical pointer dial (no power needed), 3½ digit LCD (daylight readable), or 3½ digit LED (self-illuminated). Pointer display valued in petroleum plants where operators need instant pressure confirmation during rounds.
Extended Temperature: -40 to 125°C
125°C upper limit handles high ambient near boilers, steam lines, and engine exhaust. Wider compensated range (-20 to 80°C) delivers tighter accuracy in outdoor installations with 60°C+ seasonal temperature variation.
Power Protection Built In
Reverse polarity protection prevents damage from swapped leads. Overvoltage protection guards against transient spikes from relay switching, motor starts, and lightning-induced surges. Survives real-world electrical environments.
Drop-in Replacement for Legacy Transmitters
Standard 4-20mA output and common process connections make it a direct replacement for aging Rosemount, Yokogawa, and Honeywell transmitters. Existing wiring, junction boxes, and PLC/DCS input cards work without modification.
Process Industry Applications
Petroleum Refining & Petrochemical
Reactor pressure, distillation column overhead, pump discharge, compressor suction/discharge. Ex ia II CT5 certifies for Zone 1/2 hazardous areas. HART integrates with plant-wide AMS for predictive maintenance.
Power Generation
Boiler drum pressure, feedwater pump discharge, condenser vacuum, turbine lube oil. 125°C operating temperature handles elevated ambient near boilers. Pointer display allows confirmation during operator rounds.
Pharmaceutical & Biotech
Clean utility pressure (WFI, clean steam, compressed air), reactor vessel monitoring, CIP/SIP systems. ±0.1% FS accuracy meets tighter measurement requirements of GMP-regulated batch processes.
Water & Wastewater Treatment
Distribution network pressure, filter differential pressure, pump station discharge. IP65 housing handles humid pump house environments. 4-20mA feeds directly into SCADA RTUs.
Chemical Processing
Reactor, heat exchanger, storage tank blanket, and pipeline pressure. 316L wetted parts handle most process fluids. For aggressive media (HCl, H₂SO₄), see HM50 with Hastelloy or Titanium.
Metallurgy & Mining
Hydraulic press, cooling water, dust collection, pneumatic conveying. Vibration resistance (≤±0.01% FS at 200 Hz/1g) maintains stability in high-vibration heavy industrial environments.
Dimensions & Mounting
HM25 Model Selection & Ordering Guide
Model Code: HM25 (Range) — Accuracy — Output — Connection — Options
| Selection | Code | Description |
|---|---|---|
| Pressure Type | ||
| Gauge Pressure | G (or omit) | Referenced to atmosphere |
| Absolute Pressure | A | Referenced to vacuum |
| Accuracy | ||
| ±0.4% FS | 1 | Standard |
| ±0.25% FS | 2 | High accuracy |
| ±0.1% FS | 3 | Premium accuracy (HM25 exclusive) |
| Output Signal | ||
| 4-20 mA (two-wire) | A1 | Industry standard |
| 1-5 V DC | V1 | Three-wire |
| 0-5 V DC | V2 | Three-wire |
| 0.5-4.5 V DC | V3 | Ratiometric |
| 4-20mA + HART | S | Smart intelligent, digital configuration |
| Process Connection | ||
| M20×1.5 male | F1 | Metric standard |
| G1/4 male (BSP) | F2 | British standard pipe |
| Special / Custom | F0 | Contact for availability |
| Display Options | ||
| Pointer display (0-100%) | L1 | Mechanical, no power needed |
| 3½ digit LCD | L2 | Digital, daylight readable |
| 3½ digit LED | L3 | Digital, self-illuminated |
| Additional Options | ||
| Flush Diaphragm | P | For viscous/crystallizing media |
| Intrinsically Safe | E | Ex ia II CT5 — requires safety barrier |
Example: HM25 (0–10 MPa) — 3 — S — F1 — L2 = ±0.1% FS, 4-20mA + HART, M20×1.5, LCD display.
HM25 Frequently Asked Questions
Need an Industrial Pressure Measurement Solution?
Whether you’re replacing legacy transmitters or standardizing your plant instrumentation, our engineers can help you select the right HM25 configuration. We typically respond within 12 business hours with a customized recommendation.