G.R.A.S. Type 40HT User Manual

G.R.A.S. Sound & Vibration
Single-channel Low-noise Measuring System consisting of: Type 40HT and Type 12HF - Page 6
Thechoiceofwhichfrequencyresponsetouseismadeviaatwo-positionswitchmarkedPres-
sure / Free Field on the front panel of the chosen power module (see Fig. 2.1).
Fig.1.4showstheresponsesofthetwocompensationltersaswellasthefree-eldresponse
for0°incidence.Note:free-eldcorrectionsareaddedtothelowestcurve.
Fig.1.5showswhatthesefree-eldcorrectionsareforvariousanglesofincidence.
Fig.1.6shows,foracompletelow-noisemeasuringsystem,atypicalnoiseoorin⅓-octave
bands for both the linear and A-weighted cases.
1.3 PreamplierType26HG
SimilartothestandardG.R.A.S.Type26ACbutwith40GΩinputimpedancetoenablelow-level
andlow-frequencynoisemeasurements.
Thepreamplierhasanintegrated3metrelightweightcableterminatingina7-pinLEMOcon-
nector (which plugs in to the Gain and Filter Unit Type 26HT).
A¼”to½”adapter,GR0010,isincluded,sothatitcanalsobeusedwithG.R.A.S.½”micro-
phones. See separate data sheet.
Fig. 1.4 Typical frequency response curves of Type 40HT

G.R.A.S. Type 40HT Specifications

General

Brand	G.R.A.S.
Model	Type 40HT
Category	Measuring Instruments
Language	English