Simpson 260 - Measuring Decibels

OPERATING INSTRUCTIONS
he Connect the black test lead to the grounded
side of the circuit to be measured and the
red test lead to the "hot" side.
5. Turn on the power in the circuit. Read the
output voltage on the A.C. voltage arcs of
the dial.
For the 0-2.5 V. range read the value
directly on the special arc marked 2.5
VeAeCe ONLY.
For the 10 V., 50 Ve, and 250 У. ranges
use the red arc marked A.C. and read the
black figures immediately above the arc.
6, Turn off the power in the circuit before dis-
connecting the leads.
MEASURING DECIBELS
Output voltages and audio frequency voltages
are frequently measured in terms of decibels, То
do this, proceed according to the instructions for
measuring output or AC voltage as appropriate, Read
the DB scale, which is numbered from -20 through
O to +10, and is the lowest arc on the dial.
The DB readings obtained will be correct on an
absolute scale if you are using a O DB power level
of „001 watt in 600 ohms, and if the voltage which
you read is measured across 6CO ohms.
To obtain absolute DB values across 600 ohms:
For the 10 V. range read the DB arc and
add +12 DB to the reading.
For the 50 V. range read the DB arc and
add 426 DB to the reading.
For the 250V. range read the DB arc and
add +40 DB to the reading.