23
4.15 Decibel Measurement (–20 to +50 dB)
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 260-8 serves
this purpose and is calibrated 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 on page 14.
a. Review the safety precautions in paragraph 4.2.
b. Refer to Figure 4-10 for switch settings and jack connections.
c. Use operating instructions for AC VOLTAGE MEASUREMENT, 0-2.5/10/25/
50/250V RANGES (paragraph 4.9).
Do not use the 500V or 1000V ranges for decibel readings.
d. Read decibels on the bottom scale marked dB. For the 10/25/50/250V ranges,
add the appropriate factor from the chart below:
egnaRegatloeVgnaRBgdnidaeR
V5.2-001+ot02y-ltceriddaer
V01-202+ot8g-nidaerotBd21+dda
V52-003otg0nidaerotBd02+dda
V05-603+ot6g
+nidaerotBd62dda
V052-005+ot02g+nidaerotBd04dda
NOTE: The maximum voltage ratio that can be measured is +50 dB
on the 0-250V range.
e. If dB measurements are being made to a 0.006 watt into 500 ohm reference
level, subtract +7 dB from the reading obtained on the 260.
4.16 Direct Current Measurement
• DO NOT CHANGE THE RANGE SETTING OF THE RANGE OR FUNCTION
SWITCHES WHILE THE CIRCUIT IS ENERGIZED.
• NEVER DISCONNECT TEST LEADS FROM THE CIRCUIT UNDER MEA-
SUREMENT WHILE IT IS ENERGIZED.
!
• ALWAYS TURN THE POWER OFF AND DISCHARGE ALL THE CAPACITORS
BEFORE THE SETTING OF THE SWITCHES IS CHANGED, OR THE LEADS
DISCONNECTED.
• NEVER EXCEED THE CIRCUIT-TO-GROUND VOLTAGE OF THE INSTRU-
MENT (1000 V MAX., TABLE 1-1, ITEM 16).
• ALWAYS CONNECT THE INSTRUMENT IN SERIES WITH THE GROUND
SIDE OF THE CIRCUIT.
• IN ALL DIRECT CURRENT MEASUREMENTS, MAKE CERTAIN THE POWER
TO THE CIRCUIT BEING TESTED HAS BEEN TURNED OFF BEFORE CON-
NECTING AND DISCONNECTING TEST LEADS OR RESTORING CIRCUIT
CONTINUITY.
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