GB Intsruments GMT-18A, Owner'S Manual

15

16

The decibel feature of this multimeter is for transistor gain
measurement in electronic circuits and should not be
confused with audio decibels. This function is used 
primarily by electronics technicians to measure the power 
gain in transistors, and is rarely encountered in home
project applications.

1)  Fully seat the test leads in the correct input jacks.

2)  Set the function/range switch to any one of the AC voltage

ranges and read the decibel measurement on the bottom
(red) scale of the faceplate. Based on the AC voltage
range you selected, you will need to compute the actual
measurement by using the decibel conversion chart
located at the bottom right of the faceplate.

Important: For absolute decibel measurements, circuit
impedance must be at least 600 ohms. -0- decibels = 1
milliwatt in a 600 ohm impedance (equivalent to 0.775 volts
across 600 ohms).

1)  Remove the screw in the back cover of the tester and

carefully separate the back cover from the front.

2) Note the polarity of the batteries when removing them

from their compartments and replace.

3)  Use GB catalog number GF-0306 0.5A/250V 

replacement fuses.

4)  Carefully replace the back cover and tighten the screw. 

Do not overtighten the screw as this may strip the threads
in the tester housing.

8.0 Decibel Measurement

9.0 Battery and Fuse Replacement

Order Form

Learn more about using multimeters with "How To Use 
Your Multitester For Electrical Testing and Troubleshooting".
A 160-page guide to using analog and digital multimeters.
Only available in English. Contains nine chapters of easy to
understand instructions on basic household, automotive
electrical and electronic circuit testing. Packed with
illustrations. Paperback bound. Available wherever
multimeters are sold or:

For customers within the US, send check or money order for
$15.23 per copy ($13.23 plus $2.00 per copy shipping and
handling) to:

Gardner Bender
PO Box 3241
Milwaukee, WI 53201-3241

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