HM SERIES — VACUUM & ABSOLUTE PRESSURE

HM27 Vacuum & Absolute Pressure Transmitter

Three specialized variants for vacuum and absolute pressure measurement: HM27G negative gauge, HM27A silicon absolute, and HM27CA capacitive membrane absolute — with ranges from 0.02 Pa to 1 MPa. German precision sensing elements deliver ±0.1% FS accuracy with 1/100,000 resolution for pharmaceutical, aerospace, and leak detection applications.

±0.1% FS Accuracy  |  3 Variants Measurement Types  |  0.02 Pa Min Range  |  1/100,000 Resolution

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HM27 Vacuum & Absolute Pressure Transmitter

Precision Vacuum Measurement from Germany’s advanced technology

Vacuum and absolute pressure measurement demands sensing technology that can resolve extremely small pressure changes with stability and accuracy. The HM27 addresses this with three specialized variants, each built on German HMK high-precision sensing elements tailored to specific vacuum measurement challenges.

The HM27G uses a single-crystal silicon thick-film sensor for negative gauge pressure from 0 to -100 kPa. The HM27A employs an advanced absolute pressure chip with temperature self-compensation for ranges from 5 kPa to 1 MPa absolute. The HM27CA uses the latest capacitive membrane technology for ultra-low absolute pressure measurement starting from just 0.02 Pa — where measurement is independent of media type and gas composition. For a primer on when to pick absolute over gauge or sealed-gauge, see our guide on absolute pressure vs gauge pressure.

All three variants deliver up to ±0.1% FS accuracy with theoretical resolution of 1/100,000 of full scale. Temperature drift stays within ±0.01% FS/°C (typical), and long-term stability is ±0.1% FS/year — ensuring reliable readings across seasonal temperature variations and extended deployment periods.

Three Specialized Variants

HM27G — Single-Crystal Silicon Thick Film

Negative gauge pressure: 0 to -5 kPa … -100 kPa. High-precision signal processing circuit with stable, reliable performance for general vacuum monitoring and process control.

HM27A — Advanced Absolute Pressure Chip

Silicon absolute pressure: 0 to 5 kPa … 1 MPa (Absolute). Temperature self-compensation extends small ranges to 5 kPa with higher accuracy than standard products.

HM27CA — Capacitive Membrane Technology

Ultra-low absolute: 0.02 Pa to 200 Pa / 1 Pa to 1 kPa. Measurement independent of media type and gas composition — ideal for high-vacuum and leak detection.

Choosing an HM27 vacuum pressure transmitter by range

The HM27 is a vacuum pressure transmitter family rather than a single instrument, and the right variant follows the vacuum band you actually work in. HM27G is a negative-gauge unit for suction and partial vacuum referenced to ambient air. HM27A is a silicon absolute pressure transmitter with ranges from 5 kPa up to 1 MPa, referenced to a sealed vacuum so its zero does not move with the weather. HM27CA is a capacitance thin-film absolute unit for fine vacuum, reading from 0.02 Pa.

The capacitance thin-film variant matters wherever the gas composition changes. A thermal-conductivity gauge such as a Pirani is calibrated against one gas and reads differently on argon than on nitrogen, while the HM27CA responds to the force on a diaphragm, so its reading is not affected by the species or the mixture being pumped. Wetted parts are compatible with 316 stainless steel, and an intrinsically safe Ex ia IIC T5 version is available for flammable process gases when it is powered through a safety barrier.

Below roughly 0.02 Pa, about 1.5 × 10−4 Torr, chamber base-pressure measurement belongs to dedicated capacitance manometers and ionisation gauges. The HM27 is built for process, utility, exhaust and foreline duty up to that point, delivered as a 4–20 mA signal into a PLC or DCS.

Vacuum unit equivalents across the HM27 range

Reference pointPakPaTorrmmHgpsi (absolute)
HM27CA lower limit0.020.000021.50×10−41.50×10−42.90×10−6
HM27CA upper limit2000.21.5001.5000.0290
HM27A minimum span5000537.5037.500.725
One atmosphere101325101.325760.0760.014.696

To move a specification between the units on your datasheet, use the mmHg to psi converter, psi to mmHg, torr to psi, psi to torr, or the absolute, gauge and vacuum converter.

Technical Specifications

HM27 SPECIFICATIONS
Sensing PrinciplePiezoresistive (G/A) / Capacitive Membrane (CA)
Pressure TypesNegative Gauge (G) | Silicon Absolute (A) | Capacitive Absolute (CA)
Range — HM27G0 to -5 kPa, -10 kPa, -20 kPa, -35 kPa, -50 kPa, -100 kPa
Range — HM27A0 to 5 kPa, 10 kPa, 20 kPa, 35 kPa, 100 kPa, 200 kPa, 1 MPa (Abs)
Range — HM27CA0.02–200 Pa, 1 Pa–1 kPa (Absolute)
OverloadG: 2× | A/CA: 10–100× (micro-range)
Accuracy±0.1% FS / ±0.25% FS / ±0.5% FS
Long-term Stability±0.1% FS/year (typ) / ±0.15% FS/year (max)
Zero Temp Drift±0.01% FS/°C (typ) / ±0.15% FS/°C (max)
Sensitivity Temp Drift±0.01% FS/°C (typ) / ±0.15% FS/°C (max)
ResolutionTheoretically unlimited; typically 1/100,000
Output Signal4-20 mA / 1-5 V DC / 0-5 V DC
Power Supply12–36 V DC (typical 24 V DC)
Response Time≤ 2 ms
Operating Temperature-20°C to +85°C
Compensation Temperature-10°C to +60°C
Process ConnectionM20×1.5 / G 1/4 / Clamp type
Electrical ConnectionCable IP67 / DIN 43650 plug IP65 / Aviation connector
Wetted Material316 Stainless Steel
Protection RatingIP65 (plug) / IP67 (cable)
Explosion-proofEx iaIICT5 (intrinsic safety)
Vibration Error≤ ±0.01% FS (X,Y,Z axes, 200Hz/g)

Key Features

Ultra-Fine 0.02 Pa Resolution

HM27CA capacitive membrane variant measures absolute pressures from 0.02 Pa — independent of gas type or composition. Ideal for high-vacuum semiconductor and pharmaceutical processes.

1/100,000 Resolution

Theoretical resolution of 1/100,000 of full scale enables detection of minute pressure changes in leak testing, vacuum processes, and precision scientific measurement.

German precision sensing Elements

All three variants use German HMK high-precision sensors: single-crystal silicon thick film (G), advanced absolute chip (A), or capacitive membrane (CA) technology.

Fast 2 ms Response

Sub-millisecond electrical response time captures rapid vacuum changes during pump-down cycles, leak events, and dynamic vacuum process monitoring.

Extreme Overload Protection

Micro-range absolute models withstand 10–100× rated pressure. Survives accidental venting to atmosphere without damage or permanent zero shift.

Hazardous Area Certified

Ex iaIICT5 intrinsic safety certification enables deployment in explosive atmospheres — solvent recovery, chemical vacuum distillation, and flammable vapor environments.

Applications

Pharmaceutical Vacuum Drying

Monitor vacuum levels in freeze dryers, vacuum ovens, and rotary evaporators. ±0.1% accuracy ensures consistent drying conditions for GMP-compliant pharmaceutical manufacturing.

Semiconductor Manufacturing

Ultra-low absolute pressure measurement in CVD chambers, sputtering systems, and vacuum load locks. Gas-independent HM27CA variant eliminates composition errors.

Leak Detection Systems

Detect minute pressure changes indicating leaks in sealed containers, piping, and vacuum systems. 1/100,000 resolution enables high-sensitivity testing below 1 Pa.

Aerospace & Research

Altitude simulation chambers, wind tunnel measurements, and scientific vacuum experiments requiring traceable absolute pressure readings with long-term stability.

Vacuum Distillation

Monitor vacuum levels in chemical distillation columns and solvent recovery systems. Ex iaIICT5 certification for flammable vapor environments.

Medical & Laboratory

Autoclave vacuum monitoring, vacuum packaging equipment, and laboratory vacuum manifold systems. Compact design with DIN plug or cable connection options.

Ordering Guide

Code PositionOptions
VariantG = Negative Gauge | A = Silicon Absolute | CA = Capacitive Abs
Range (G)0~-5kPa | -10kPa | -20kPa | -35kPa | -50kPa | -100kPa
Range (A)0~5kPa | 10kPa | 20kPa | 35kPa | 100kPa | 200kPa | 1MPa
Range (CA)0.02~200Pa | 1Pa~1kPa
Accuracy1 = ±0.5% | 2 = ±0.25% | 3 = ±0.1% FS
OutputA1 = 4-20mA | V1 = 1-5V | V2 = 0-5V
Process ConnectionF1 = M20×1.5 | F2 = G1/4 | F3 = Clamp
Electrical ConnectionW1 = Cable IP67 | W2 = DIN plug IP65 | W3 = Aviation connector

Example: HM27-A-0~100kPa-2-A1-F1-W2 = Silicon absolute, 0–100 kPa, ±0.25% FS, 4-20mA, M20×1.5, DIN plug.

HM20 General Purpose Pressure Transmitter

HM20 General Purpose Transmitter

Versatile 4-20mA pressure transmitter for general industrial applications. Wide range coverage with robust design.

HM22 High-Accuracy Pressure Transmitter

HM22 High-Accuracy Transmitter

0.075% FS accuracy with advanced digital compensation. Ideal for precision measurement applications.

HM25 Industrial Pressure Transmitter

HM25 Industrial Pressure Transmitter

Rugged industrial transmitter with HART protocol support. Built for demanding process environments.

HM26 Ceramic Capacitive Pressure Transmitter

HM26 High Temperature Transmitter

Ceramic capacitive sensing for high-temperature applications up to 150°C. 0.1% FS accuracy.

Frequently Asked Questions

Choose HM27G for negative gauge pressure (vacuum relative to atmosphere). Select HM27A for absolute pressure referenced to perfect vacuum in the 5 kPa–1 MPa range with temperature self-compensation. Use HM27CA for ultra-low absolute pressure from 0.02 Pa where gas-independent measurement is critical — such as semiconductor CVD, leak detection, and high-vacuum scientific applications.

Yes. The capacitive membrane principle measures pressure through diaphragm deflection, which is independent of gas molecular weight, composition, or viscosity. This makes the HM27CA ideal for mixed-gas environments and processes where gas composition varies — unlike thermal conductivity gauges (Pirani) that require gas-specific calibration.

The HM27 is designed for this scenario. Micro-range absolute models (HM27A and HM27CA) have overload capacity of 10–100× rated pressure, so accidental venting to atmosphere causes no damage or permanent zero shift. The HM27G gauge variant supports 2× overload protection.

With 1/100,000 resolution, the minimum detectable change depends on the selected range. For a 0–35 kPa absolute range, resolution is approximately 0.35 Pa. On the HM27CA 0.02–200 Pa range, resolution is approximately 0.002 Pa — enabling detection of extremely small leaks and vacuum fluctuations.

The standard HM27 provides analog output (4-20mA, 1-5V, 0-5V). For RS485 Modbus or HART digital communication, please contact our engineering team about custom configurations or consider the HM25 industrial transmitter with HART protocol support.

Need a Vacuum or Absolute Pressure Solution?

Tell us about your application requirements. Our engineers will recommend the best HM27 configuration for your process conditions — typically within 24 hours.

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