(1) The PERCENT INPUT meter indicates the battery condition.
The pointer
should fall within the BAT OK region of the meter scale.
It is also the search
indicator which indicates the percentage of input of the range selected.
If the
input is from 50 to 100 percent of the range selected, the pointer will be in a
green band; if the input is 100 to 150 percent of input, the pointer will be in the
red area of the meter scale.
(2) The galvanometer is the null indicating device which is used to
determine the balance between the variable difference voltage and the DC output
from the thermocouple.
The SENSITIVITY switch selects the sensitivity of the
galvanometer; LOW, MED, or HIGH.
In the center of the SENSITIVITY switch is the
GALV ZERO, this is the electrical zero control for the galvanometer.
Initial
setting of the sensitivity switch should be on LOW.
(3) The GALV switch electrically connects the galvanometer circuit between
the thermocouple output and the variable internal reference supply when in the LOCK
or MOMENTARY positions. The GALV switch is briefly pushed from OPEN to MOMENTARY
to determine if the galvanometer will indicate on scale.
After an on scale
indication is obtained, the GALV switch may be set to LOCK.
(4) The SENSITIVITY TEST switch is used to determine the amount of
deflection of the galvanometer for 0.1 percent and 0.01 percent changes in input.
(5) The three REFERENCE adjust controls; COARSE, MEDIUM, and FINE, vary the
reference voltage for galvanometer balance.
(6) There are two pair of input connectors, DC and AC.
The DC binding
posts are provided for connecting DC voltage to the Model 540B. The positive lead
must be connected to the upper post and the negative lead to the lower post
(chassis ground). AC voltages may be applied to the AC connector, either through a
UHF-type connector or a standard dual banana plug.
(7) The RANGE switch selects the proper dropping resistor and compensating
network for measurements of voltage up to and including the voltage indicated; this
may be AC or DC.
(8) The MODE switch selects SEARCH or TRANSFER modes for either AC or DC
input to the instrument. Range selection is made in the SEARCH modes by selecting
a voltage range that gives a PERCENT INPUT meter indication between 50 and 100
percent.
(9) The POLARITY is a push button switch used to reverse the input to the
thermocouple.
This facilitates measurement of the reversal error to the
thermocouple.
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