Related Manuals for G.R.A.S. 41AM
Summary of Contents for G.R.A.S. 41AM
- Page 1 G R A S SOUND & VIBRATION Skovlytoften 33, 2840 Holte, Denmark www.gras.dk gras@gras.dk...
- Page 2 Outdoor Microphone System Types 41AM / 41CN Note: unless individually specified, the term “Outdoor Microphone System” throughout this document refers to both types, i.e. Type 41AM and Type 41CN. Revision 11 June 2010 LI0002...
- Page 3 Important! any dismantling details given in this document are addressed solely to qualified service personnel who must ensure that the unit is first disconnected from its power supply before pro- ceeding.
-
Page 4: Table Of Contents
CONTENTS Introduction and Description........5 Available Types and Applications . -
Page 5: Introduction And Description
G.R.A.S. Sound & Vibration Introduction and Description The G.R.A.S. Outdoor Microphone System (Fig. 1.1) is for outdoor use whenever trouble-free noise monitoring is required, e.g. around airports or in communities. It complies with IEC 651 Type 1 and ANSI S1.4 1983 Type 1 requirements and can be used with any suitable electronic sound or vibration measurement system. -
Page 6: Available Types And Applications
Outdoor Microphone System. Types, reference directions and applications Available Types and Applications There are two types of the Outdoor Microphone System, these are Type 41AM and Type 41CN. Each has its own measurement reference direction and application, i.e.: Type 41AM ... -
Page 7: Main Components
G.R.A.S. Sound & Vibration Main Components The following is a brief description of the main components of the Outdoor Microphone System (see also Fig. 2.1). All external metal parts are made of stainless steel. Windscreen and windscreen holder with anti-bird spikes. ... - Page 8 G.R.A.S. Sound & Vibration Anti-birds spikes Windscreen and holder Electrostatic actuator ½″ microphone Preamplifier Equalisation vent Dehumidifier inspection window Calibration oscillator Lin. or A-weighting Sensitivity control 0 or ±20 dB gain Cable driver DC - DC converter Dehumidifier Pole adapter LEMO connectror Tripod adapter 12 - 18 V DC...
-
Page 9: Windscreen
This comprises a windscreen and a windscreen holder (see Fig. 2.3). The windscreen itself is made of polyurethane foam. It reduces wind-noise to a minimum and gives maximum rain protection. It also allows for 0 ° (Type 41AM) and 90 ° (Type 41CN) refer- ence directions of incidence. -
Page 10: Pressure Equalisation
G.R.A.S. Sound & Vibration Type 41CN Rain-protection cap and actuator Teflon sleeve Pressure-equalisation tube Type 41AM Add silicone grease to this thread Transport tube Dehumidifier inspection window Fig. 2.4 Showing microphone assembly - note the difference between the two rain-protection caps 2.2.1... -
Page 11: Dismantling The Microphone Assembly
Remove the black cone from the top of the rain-protection cap (Type 41CN only). Unscrew the mushroom-head screw holding the Teflon rain-protection cap in place. for the Type 41AM and for the Type 41CN. Note: Left-hand thread - unscrew clockwise. -
Page 12: Access To Electronics Assembly
G.R.A.S. Sound & Vibration Access to Electronics Assembly For access to the electronics assembly, do the follow- ing. The circled numbers refer to which part of the tool Retaining ring AM0038 (Fig. 2.5) to use: Unscrew the large retaining ring at the base of the casing Make sure that only the retaining ring turns. - Page 13 G.R.A.S. Sound & Vibration Remove the silica-gel container. Dehumidifier At this point, the silica-gel crystals can be container removed from the container, dried off and used again (see section 5.2). Unscrew the stainless-steel casing to give access to the electronics assembly. If necessary, remove the screw from the dehu- midifier inspection window and screw the tommy bar (AM0063) in its place if the casing is difficult...
-
Page 14: Calibration
G.R.A.S. Sound & Vibration Calibration Electrostatic Actuator The Outdoor Microphone System is equipped with a built-in electrostatic actuator to enable rapid calibration checks in-situ. The electrostatic actuator is factory adjusted to simulate a sound level of 90 dB at a frequency of 1000 Hz on the diaphragm of the microphone (94 dB is also available on order). -
Page 15: Pistonphone
Once the windscreen has been removed, mount the adapter as follows (refer to Fig. 4.2): Fig. 4.2 Mounting the Adapter RA0009/RA0041 The Adapter RA0009/RA0041 is not included with the Outdoor Microphone System Type 41AM/41CN but is available on sepa- rate order. Outdoor Microphone System - Page 15... -
Page 16: Setup And Adjustment
G.R.A.S. Sound & Vibration 4.2.1 Setup and adjustment Screw the support tube (1), with its collar (2) on, onto the thread used by the windscreen. If the adapter has not been used recently, the collar might stick a little and should be made free before proceeding. -
Page 17: Maintenance
G.R.A.S. Sound & Vibration Maintenance Windscreen The windscreen should be cleaned as and when necessary depending on the severity of local conditions. Recommended exchange frequency is one year. First remove the foam inner sleeve and thereafter unscrew the windscreen assembly and lift it over the top of the microphone assembly. -
Page 18: Multi-Frequency Calibration Check (Optional)
G.R.A.S. Sound & Vibration Multi-frequency Calibration Check (Optional) This makes use of an option which calls for an internal modification of the Outdoor Microphone System. This option allows an AC signal of approximately 1 V RMS to be applied to pin 4 shown in Fig. -
Page 19: Service And Repair
G.R.A.S. Sound & Vibration Service and Repair Service and repair should be carried out only by qualified service personnel. The Outdoor Microphone System should not be dismantled with power on because of the presence of high voltages in its circuits. Outdoor Microphone System - Page 19... -
Page 20: Specifications
G.R.A.S. Sound & Vibration Specifications Valid for Types 41AM/41CN at 1013 mbar, 23 °C and 50 % RH unless stated otherwise Nominal sensitivity: 50 mV/Pa Frequency response: IEC 651 Type 1 and ANSI S1.4-1983 Type 1 For the applicable reference direction as shown in Fig. 1.2, re. 1000 Hz: 20 Hz - 80 Hz: ±... - Page 21 Tripod adapter: AM0033 Pole adapter: AM0029 LEMO plug FFA.2S.306: AE0001 Silicone grease (7-ml tube) MI0016 Accessories available: Pistonphone adapter: RA0009 (Type 41AM) RA0041 (Type 41CN) Foam windscreens (5 items): AM0009 Calibration Control Box: AC0001 Extension cables: AA0003 10m: AA0002 20m:...
-
Page 22: Circuit And Component Diagrams
G.R.A.S. Sound & Vibration Circuit and Component Diagrams Fig. 8.1 shows the circuit diagram for signal conditioning. Fig. 8.2 shows the circuit diagram for the power supply. Fig. 8.3 shows component placement and the location of user-serviceable jumpers and adjust- ment potentiometers. - Page 23 G.R.A.S. Sound & Vibration Outdoor Microphone System - Page 23...
- Page 24 G.R.A.S. Sound & Vibration Outdoor Microphone System - Page 24...
- Page 25 G.R.A.S. Sound & Vibration Outdoor Microphone System - Page 25...
Need help?
Do you have a question about the 41AM and is the answer not in the manual?
Questions and answers