Fluke 540B - Troubleshooting; General; Thermocouple Replacement

540B
REVERSAL ERROR CORRECTION
540B
STANDARD
UNDER
TEST INSTRUMENT
DC NORMAL
ZERO
ZERO
DC REVERSED
+4 SD
-6 SD
540B
UND ER TEST
CORRECTED ZE RO (NORMAL}
-2 SD +3 SD
-
-
DC t
: Ac
Input
Input
TRAN SFER CAL IBRATION CHECK
540B
Test Re po rt
Corre ct ed
Under
Te st
Corrections
Erro r
.
01 % Deflection
8
SD
DC COAX
COAX
AC
7 SD
*
SOURCE
"T" "T" SOURCE
P e rcent/D i vision
. 001% .001%
50 Hz
Devia tion +3 SD
%Dev iation +. 004%
+ . 002% +. 006%
STANDARD
50 kHz Deviation
- 16
SD
TRANSFER INST.
--- , r - --
% Deviation -. 023% + .01 % -. 013%
DC AC
Input Input
1 MHz Deviation
+2 8 SD
%Devi ation
+.04% -. 02% +.02%
* Dev iati on for standard transfer instrum en t.
Figure 4 -5 . TRANSFER CALl BRA TION CHECK
i. Switch both standar ds to the AC TRANSFER MODE
and adjust the ac source lev el for a true zero reading
on the
standar d system galvanom eter. Do not adj us t
the reference contr ols or l indeck of ei ther sy stem
while
in th e AC MODES.
j. Operate the GALV switch to LOCK and read the
deflect io n of the ga l vanometer on the 540B being
check ed. (Left deflection is + and right deflection
is -).
k. Sw itch both transf er systems back to DC TRANSFER
MOD E to determine if the de level has drifted. If
both systems do n ot return to the settings made in
st ep g, it will be necessary to repeat th e transf er
p
ro cess starting with step g. st e ps g thru k w il l
have to
be repeated until a finite degr ee of repe at -
abil ity is att a ined. This is usually considered to
be thr ee near identical readings in a total of four
att empts . After obtaining a series of near ide ntical
reading s enter th e averag e on the test record and
comput e the perc ent of deviation fr om zero. Add
th e figure just compu ted and the Tes t Report c or -
recti on for the standard instrument. The sum will
equal the
corrected error and may be entered in the
space provided in the test record.
l. Steps f thru k will have to be repe a ted for every
frequency to be checked. Should th e instrument f ail
calibr ation check in the 0. 5 volt range, it is reason -
able to assume that all ranges will be in erro r, as
pointed out in Section 4-21. In this case it will be
necessary to return the instrument to the facto ry or
some other facil ity capa ble of recalibrating the
540B.
m.
Ste ps a thru 1 will have to be re peated for ever y
range or vol tage to be checked.
4-36. TROUBLESHOOTING
4 -37. GENERAL
4
-38. The Model 540B must have a complete set of
batteries that a re within the lim it s given in the ba ttery
che ck range . Low voltage from t he batteries w ill re-
sult in a variety of trouble indications, including com-
plete failur e of the instrum ent. If ther e is any .. doubt as
to the adequacy of the batteries to supply sufficient volt-
age they s hould be changed before any other correctiv e
action is taken.
4-39. THE RM OCOUPLE REPLACEMENT
4-40. Should the thermocouple become damag ed , re-
p laceme nts are av ailable from the factory. However,
to realize the fu ll accuracy capability of the instrument ,
the Model 540B should be returned to the factory for re-
calibration.
C AUTION!
If for any rea s on any of the compon ent s or
wiring in that portion of th e circuit between
the input terminals and the thermocouple,
are changed or moved it will be ne ces sary
to rec ali brate the Model A54. Any changes
in
this protion of the circuit can ca use large
calibr ation changes in the higher frequency
trans fers .
4-7