GRAS 40SA Probe Microphone
Freq range: 2 Hz to 8 kHz
Dyn range: 40 dB(A) to 166 dB
Sensitivity: 3 mV/Pa
The GRAS 40SA Probe Microphone is a small, compact unit for sound-pressure measurements in small enclosures, in harsh environments and in very close proximity to sound sources. The high acoustic input impedance at the tip of the probe minimizes its influence on the acoustic field, while the stainless-steel tube of the probe can withstand temperatures of up to 800 ºC.
Technology
Typical applications and use
- Acoustic-impedance measurements
- Exhaust-system measurements
- Near-field measurements
- Measurements at high temperatures
- Pressure-distribution measurements in smallenclosures
Design
The GRAS 40SA is constructed with detachable stainless-steel probe tubes which guide the acoustic signal to a microphone inside the housing of the 40SA. After being sensed by the microphone, the acoustic signal is passed on to an impedance matching wave guide which eliminates unwanted internal reflections. The result is a smooth frequency-response ranging from 2 Hz up to 20 kHz. The internal microphone is connected to a low-noise preamplifier with a high dynamic range; ensuring a measurement range from approximately 40 dB to 166 dB re. 20 μPa. The data sheet shows the preamplifier’s connections via its LEMO plug.
The GRAS 40SA Probe Microphone is internally compensated to equalize the internal pressure of the microphone with the static pressure at the probe’s tip . The static pressure within the 40SA will therefore adjust itself to the static pressure existing at the probe’s tip; which it does with a time constant of approximately 0.1 s.
The 40SA can be used with various probe lengths and is delivered with four standard probe lengths, i.e.: 20 mm, 40 mm, 80 mm and 160 mm. Intermediate lengths can be made by cutting these standard lengths. Also, the stainless steel tubes can be bent to a radius as low as 5 mm without downgrading the system’s acoustics. A flexible probe tube is also provided for use in measurements where stiff stainless-steel tubes are not practical. This does, however, slightly downgrade the system’s acousticperformance.
The right angled design of the 40SA makes it particularly well suited for measurements on exhaust-gas systems and other machinery in general as well as for scanning vibrating surfaces such as loudspeaker diaphragms and cabinets.
The compact size, low weight and all-stainless-steel construction of the 40SA make it robust, easy to handle and easy to mount.
The 40SA is provided with a 3 m integrated cable with a 7-pin LEMO connector. Extensions cables are available.
Specifications
Frequency response for various lengths of stainless-steel probes
GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.
Dimensions
Length (housing): 83.8 mm
Diameter: 12.7 mm
Probe tube outside diameter: 1.25 mm
Probe tube inside diameter: 1 mm
Ordering info
Included items
GRAS GR0265 | Pistonphone adapter for stainless steel probe |
GRAS GR0266 | Pistonphone adapter for flexible probe |
GRAS GR0267 | Heat sink and tool |
GRAS RA0326 | Calibration coupler |
GRAS GR0263 | 1.3 mm insert pin for calibration coupler |
GRAS GR0266 | 1.6 mm insert pin for calibration coupler |
GRAS YY0004 | Pair of pliers |
GRAS YY0005 | File |
GRAS MI0016 | Silicon grease |
GRAS EK0018 | Teflon tubing (L=0.5 m, Dia.: 1.6 mm) |
GRAS GR0258 | 20 mm probe tube |
GRAS GR0259 | 40 mm probe tube |
GRAS GR0260 | 80 mm probe tube |
GRAS GR0261 | 160 mm probe tube |
GRAS GR0401 | Flexible probe tube |
GRAS SK5546 | Needle for cleaning |
Optional items
| GRAS AA0008 | 3 m LEMO 7-pin - LEMO 7-pin Cable |
| GRAS 12AA | 2-Channel Power Module with gain, filters and SysCheck generator |
| GRAS 12AQ | 2-Channel Universal Power Module with signal conditioning and PC interface |
| GRAS 42AA | Pistonphone, Class 1 |
| GRAS 42AP | Intelligent Pistonphone, Class 0 |
GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.
