Fluke 540B - Precautions

540B
REF
NAME
REF
FUNCTION
NR.
DESIG
13
SHUNT
J 805
Binding
posts provided to accept the Fluke Model A40
J 806
Current Shunts. A locking screw for the larger shunts
is provided and is locat ed on the rear panel of the Model
A54
plug-in unit.
Without a Model A40
plug-in the i nstru-
ment has a basic current range of 2. 5 to 5 ma.
14
DC INPUT J 801
Binding posts, with centers 3/ 4 inch apart, are provided
J 803 for connecting de voltage to the A54. Connect the positive
lead to the upper post. The lower post is chassis ground.
15 AC INPUT
J 802 A dual purpose AC INPUT connector arrangem ent is pro-
J 804 vided in the .Model A54. AC voltages may be applied to the
unit through the UHF type connector or, since a separate
ground post is located 3/4 inch from the UHF connector's
center, a standard dual banana plug.
16 PROTECTION DISABLE
s 803 Disconnects the diode protection circuit in parallel with the
(Model A54-2 only)
thermocouple, when depressed . Depression of the switch,
while at null (zero) on the GALVANOMETER meter in the
AC TRANSFER mode, will cause a deflection.
If the de-
flection at each frequency and on each range of interest is
noted periodically, the change in deflection will then be an
indication of the long term stability performance of the
transfer portion of the unit including the protective cir-
cuitry.
17
PANEL BUSHING
NONE
An internally threaded bushing used in conjunction with
the current shunt retaining screw.
Figure 2 -2 . FRONT-PANEL CONTROLS, TERMINALS, AND INDICATORS (Sheet 2 of 2)
2-5. Should lesser degrees of accuracy suffice for any
application, the specifications for auxiliary equipment
as shown in Figure 2-3 may be reduced. For additional
application information contact your Fluke
repres enta -
tive or the factory.
2-6 . METHODS OF OPERATION
2-7. There are many different methods of making
accurate transfer measurements. The methods outlined
in this manual are suggested as being adequate. Infor-
mation about
transfer measurements, methods, theory,
etc. may be found in the following references:
a. THERMAL CONVERTERS AS AC-DC TRANSFER
STANDARDS FOR CURRENT AND VOLTAGE MEAS-
UREMENTS AT AUDIO FREQUENCIES, F. L.
Hermach, J. Research 48, 121 (1952} RP2296.
b. A WIDE-RANGE
VOLT - AMPERE CONVERTER
FOR CURRENT
AND VOLTAGE MEASUREMENTS,
AlEE Transactions, Communications and Elec-
tronics, Paper No. 59-161 (1959}. F. L. Hermach
and E. S. Williams.
c. CALIBRATION OF VOLT-AMPERE CONVERTERS,
National
Bureau of Standards Technical Note 188,
(1963} E. S. Williams.
2-8. PRELIMINARY OPERATION
2- 9. PRECAUTIONS
2-10. High
order accuracy can be obtain ed with this
Transfer Standard only if the user is aware of certain
limitations and takes appropriate precautions as follows:
a. Bead type thermocouples, like that used in the Model
540B, exhibit a
small exponentially decreasing drift
of emf after a steady heater current is initially
applied. Allow approximately 10 minutes for the
thermocouple element to stabilize. After the stabi-
lization time, the drift should be less than 2 small
divisions per minute in the HIGH sensitivity position.
When
changing to different levels of input, after
the stabilizati on period, a wait of only a few minutes
is necessary before continuing with measurements.
Any observed drift should be evaluated quanti -
tatively.
b. Connection errors should be evaluated and min i-
mized when the Transfer Standard is used to cali -
brate other instruments. These errors can often
be
detected by changing the length and position of
the
leads. Short coaxial leads should be used when
possible. These errors can be significant at high
test frequ encies .
2-3