11
LI0056 – Revision 28 May 2015
Separate Calibration
You can calibrate the microphone in-situ as described on page 10, but you can also
calibrate it separately. In this case, no correction factor is needed.
To calibrate the microphone, you must remove it from the probe tube:
1. Open the blast probe as described on page 7.
2. Pull out the microphone assembly as described on page 8.
3. Mount the Calibration Adapter RA1423 in the pistonphone.
4. Place the blast probe tube next to the pistonphone. Do not attempt to remove
the microphone cable from the tube.
5. Push the microphone all the way down into the adapter so that it is sealed by
the O-ring inside the adapter.
6. Turn on the pistonphone.
G.R.A.S.
Pistonphone
Type 42AP
Serial No. XXXXX
IEC 60942 (2003) LS
Signature Series
Pistonphone 42AP
1/2” to 1/8” adapter
RA1423
67SB Blast
Probe Microphone
Serial No. XXXXXX
G.R.A.S.
Blast probe -
rear end
Fig. 11.
Typical calibration setup using The G.R.A.S. pistonphone 42AP.