Simpson 270 Series - Page 41

Operation
` d. Turn power OFF.
e. Connect the test leads across the circuit being measured with
the black test lead to the ground side.
f. Turn on the power in the test circuit. Read the output voltage
on the appropriate AC voltage scale. For the 0-2.5V range,
read the value directly on the scale marked 2.5 VAC. For the
10У, 50V, or 250V ranges, use the red scale marked AC ‘and
read the black figures immediately above the scale.
4.13 DECIBEL MEASUREMENT (—20 to +50 dB)
4.13.1 In some industries, measurements are made in terms of
voltage or current ratios (decibels) based on a specific reference
level. The dB scale on the 270 serves this purpose and is cali-
brated to a reference level (zero dB) of 0.001 watt into 600 ohms.
The scale calibration of —20 to +10 dB is for the 0-2.5V range
(zero dB = 0.775V). Higher ranges may be used by adding an
appropriate dB value to the reading in accordance with the chart
below.
a. Review the safety precautions in paragraph 4.2.
b. Refer to Figure 4-6 for switch settings and jack connections.
c. Use operating instructions for AC VOLTAGE MEASURE-
MENT, 0-2.5/10/50/250/500V RANGES (paragraph 4.10).
Do not use the 500V range for decibel readings.
d. Read decibels on the bottom scale marked dB. For the
10/50/250V ranges, add the appropriate factor from the chart
below:
Voltage
Range dB Range Reading
0- 2.5V —20 to +10 read directly
0- 10 V - 8 to +22 add +12 dB to reading
0- 50 V + 6 to +36 add +26 dB to reading
0-250 V +20 to +50 add +40 dB to reading
4-15