G.R.A.S. 40LA 1/4" CCP Precision Surface Microphone, High Pressure

Freq range: 5 Hz to 70 kHz
Dyn range: 56 dB(A) to 178 dB
Sensitivity: 0.5 mV/Pa

Typical applications and use

  • Aerospace industry
  • Wind-induced noise analysis on airplanes
  • In-flight measurements
  • Wind-tunnel testing
  • Acoustic-fatigue testing


Just 2.5 mm thick, the 40LA has an integrated CCP preamplifier and is delivered with a built-in TEDS chip, which enables it to be programmed as a complete unit.

The 40LA requires a constant-current power supply, such as the G.R.A.S. 12AL CCP Supply or any other CCP compatible power supply. Close manufacturing tolerances, together with the advantages of the TEDS chip, provide the 40LA with a high degree of interchangeability; a major advantage which excludes accounting for individual characteristics.

The 40LA is both very stable and robust. It has an integrated 1.5 m coaxial cable with a Microdot connector and is delivered with a supple, detachable silicon-rubber fairing. G.R.A.S 40LA is also available with customized cable lengths – see Ordering info for more options.

Because of its lightness, the microphone with fairing can readily be mounted on surfaces using double-sided adhesive tape. The broad temperature range makes the 40LA well-suited for the aerospace industry.

All G.R.A.S. microphones are individually checked and calibrated before leaving the factory. An individual calibration chart is supplied with each microphone.


When leaving the factory, all G.R.A.S. microphones have been calibrated in a controlled laboratory environment using traceable calibration equipment. Depending on the use, measurement environment and internal quality control programs we recommend that the microphone is recalibrated at least once a year.

We offer two kinds of calibration as an optional after-sales service: G.R.A.S. Traceable Calibration and G.R.A.S. Accredited Calibration.

G.R.A.S. Traceable Calibration is a traceable calibration performed by trained personnel under controlled conditions according to established procedures and standards. This is identical to the rigorous calibration that all G.R.A.S. microphones are subjected to as an integral part of our quality assurance.

G.R.A.S. Accredited Calibration is performed by the G.R.A.S. Accredited Calibration Laboratory that has been accredited in accordance with ISO 17025 by DANAK, the Danish Accreditation Fund.

If you want a new microphone set delivered with an accredited calibration in stead of the default factory calibration, specify this when ordering.

Learn more at gras/calib.

Quality and warranty

G.R.A.S. microphone sets are made of components from our proven standard portfolio and are all manufactured of high-quality material and branded parts that were chosen and processed to ensure life-long stability and robustness.

All parts are manufactured and assembled at the factory in Denmark by skilled and dedicated operators in a verified clean-room environment. The microphone diaphragm, body and unique protection grid are made of high-grade stainless steel and make the microphone set resistant to physical damage as well as corrosion caused by aggressive air or gasses.

This, together with the enforced gold-plated microphone terminal guarantees a highly reliable connection. Thanks to the high quality, our warranty against defective materials and workmanship is 5 years.


Should you by mistake damage the diaphragm on a G.R.A.S. microphone we will in most cases be able to exchange it at a very reasonable cost and short turn-around time. This not only protects your investment but also meets your quality assurance department since you do not have to worry about new serial numbers etc.

Frequency range (±1 dB) Hz 10 to 20 k
Frequency range (±3 dB) Hz 5 to 70 k
Dynamic range lower limit (microphone thermal noise) dB(A) < 56
Dynamic range upper limit with G.R.A.S. CCP preamplifier dB 178
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 0.5
Polarization voltage V 0
Power supply (Constant Current Power) mA 2 to 20
Microphone venting Front
Output impedance Ω <50
Temperature range, operation °C / °F –55 to 100 / -67 to 212
Temperature range, storage °C / °F -40 to 85 / -40 to 185
TEDS UTID (IEEE 1451.4) 27 v. 1.0
Connector type Microdot 10/32
CE/RoHS compliant/WEEE registered Yes / Yes / Yes
Weight g / oz 3 / 0.101

Typical pressure frequency response


G.R.A.S. GR0933 Adhesive tape, pre-cut, single-sided
G.R.A.S. GR0934 Adhesive tape, pre-cut, double-sided
G.R.A.S. MI0031 Cleaning tissue
G.R.A.S. AE0046 Adapter, BNC male to Microdot female
G.R.A.S. GR1252 Silicon-rubber fairing


1/4" Precision Surface Microphone with customized cable length, high pressure. Specify the length in cm. (e.g. 40LA-CL0350 specifies a 350 cm  cable (3.5 m)). Maximum cable length is 5 meters.
G.R.A.S. 12AQ Power Module (2-ch.)
G.R.A.S. 42AP Intelligent Pistonphone with built-inprecision barometer (250 Hz or 251.2 Hz,114 dB ±0.05 dB) (recommended)
G.R.A.S. 42AA Pistonphone(250 Hz, 114 dB ±0.08 dB)
G.R.A.S. GR1297 Aluminum fairing
G.R.A.S. OP0025 Kit for Sensitivity Calibration of Surface Microphone Sets
G.R.A.S. OP0026 Kit for Frequency Calibration of 1/4" Surface Microphone Sets

G.R.A.S. CA0029

Traceable Calibration of Microphone Set

G.R.A.S. CA2301

Accredited Calibration of Microphone Set