G.R.A.S. Sound & Vibration
Single-channel Low-noise Measuring System consisting of: Type 40HT and Type 12HF - Page 5
Fig. 1.3 shows a Single-channel Low-noise Measuring system (as described in this document)
and consists of:
•
½-inch Low-noise Level Microphone System Type 40HT.
•
Power Module Type 12HF.
Note: the power module must be ordered separately and the tripod and tripod adapter are
optional extras.
1.1
Microphone Type 40AH
The Type 40AH is a special high-sensitive ½-inch microphone. It is externally polarized with
a specially reduced inherent noise floor in order to achieve a high dynamic range and wide
frequency range.
1.2
Gain and Filter Unit Type 26HT
The body of the Unit has an overload-warning LED, (Fig. 1.1), which is repeated on the front
panel of the chosen power module (see Fig. 2.1).
The signal of the microphone is amplified by 20 dB in the Gain and Filter Unit Type 26HT.
The two compensation filters give the system two parallel outputs which correspond to:
a)
linear pressure-frequency response.
b)
linear free-field frequency response at an angle of 0 ° incidence.
Fig. 1.2 Power modules available from G.R.A.S. for Type 40HT,
Left: Single-channel Power Module Type 12HF
Right: 10-Channel Module Type 12HM
Fig. 1.3 A Single-channel Low-noise Measuring System as described
in this document, shown here with Tripod and Tripod Adapter
(both available from G.R.A.S.)
To Analyser
Type 12HF
Type 40HT
