Posted in | Acoustic Sensor

High Intensity Acoustic Sensors: Models 765M25 & 765M27

The High Intensity Acoustic Sensors (Microphones) Models 765M25 and 765M27 are developed for the monitoring of gas-borne sound in industrial applications. These sensors are compatible with type 316 stainless steel diaphragms and are designed for usage in corrosive settings. Only the electrical connections separate the two designs.

A small 10-32 fused-glass coaxial connector is included in the Model 765M25, whereas the Model 765M27 has a 2-pin connector interface. Both devices provide a fully hermetic seal when paired with their all-welded construction.

Electrically, these devices use piezoceramic sensing components in a balanced and floating design to enable improved rejection of electrical noise observed in many industrial settings. When utilized with a real differential input amplifier, the best results are obtained.

For interface or customized versions of this sensor, contact the manufacturer.

  • High temperature to +500 Deg F
  • High sensitivity (1200 pC/psi)
  • Choice of electrical interface
  • Electrically isolated



Table 1. Source: Columbia Research Laboratories, Inc.

Transfer / Electrical 765M25 765M27
Charge Sensitivity 1200 +/-200 pC/psi
Frequency Response 2 Hz To 8,000 Hz
Dynamic Range 0.28 x 10-4 to 10 psi (191 dB SPL Max.)
Avg Temp Coeff of Sensitivity 0.08% / Deg F Nominal
Transducer Capacitance 6,300 pF +/-10%
Insulation Resistance 100 Megohms Min., 50 VDC Test
Isolation Resistance 100 Megohms Min., 50 VDC Test
Dielectric Strength 550 Vrms, 60 Hz, Element to Housing



Table 2. Source: Columbia Research Laboratories, Inc.

Environmental 765M25 765M27
Vibration Limit 100 g Max. (Sine)
Shock Limit 1,000 g Max., 0.25 mSec
Temperature Range -10 To +500 Deg F (-23 To +260 Deg C)
Humidity1 0 To 100% R.H.
Static Pressure 3,000 psi Max. (Diaphragm)
Electromagnetic Sensitivity 0.005 g (Equiv / 100 Gauss)



Table 3. Source: Columbia Research Laboratories, Inc.

Physical 765M25 765M27
Configuration Balanced Floating Compression
Model 765M25
Model 765M27

1.375 In. Hex. x 1.88 In. H (35.0 mm Hex x 47.8 mm H)
1.375 In. Hex. x 2.10 In. H (35.0 mm Hex. x 53.34 mm H)
Weight 7.0 Oz (200 Gm)
Body & Diaphragm
Type 316 Stainless Steel
Electrical Interface Isolated 10-32 Coaxial Connector 2-Pin MIL-C-5015 Style Connector
Mounting 1.125 – 12 UNF-2A Straight Thread


NOTE: 1 The unit is hermetically sealed when the connector is mated or protected.

High Intensity Acoustic Sensors: Models 765M25 & 765M27

Image Credit: Columbia Research Laboratories, Inc.

Accessories Supplied

  • Standard Calibration Data
  • Low Noise Cable Assembly (3M) (300 pF) - Model 765M25 Only
  • Hardwood Storage Case

Other Equipment by this Supplier

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