jar
°
RESISTANCE CALIBRATION OF AN=PDR=39's
The Tl-B or POR-39 instrmeents rely on the accuracy of their hi-meg or
chamber load resistances for scale decadings
A Single calibration control
(meter serias resistance) performscalibration of all scales at onctes
It was felt that some method of assuring hi-mag accuracy should be used tc
check all instruments before they met Meld usa.
It was also felt that the
Victoreen deposited carbon hi-meg resistances might be highly voltage sensitive
and should be checked under circumstances approximating their actual operating
potentials.
Commercial hi-meg ohm meters often use potentials up to 1000 volts
making them unsuitable for this applicatione
An Applied Physics Corp. vibratin
reed electromster was used to measure the potential across a 100 megohm standar
resistance (calibrated to value f .3%) in series with the uninam hi-meg (in pl
in the instrumnt).
All resistors varying more than 5% were replaced,
to calibrate the 0 to § mr, range was madee
No atte
¢ aphed
The standard Bendix bridge and sub miniature tube tester'by the Arny for u
with the instruments uses a potential of 16 volts across the unknown resistance
It 1s felt that the Bendix unit serves tha purpose well - better perhaps than 4
electrom ter technique which is of a laboratory natures
For most accurate results each instrument should be calibrated on the scali
representing the mean deviation (since each scale varies 4 a few percent).
was not available for this purpose,
Tim
Each T1-3 carries within it a card giving
the deviations for future use.
The POR-39 schematic places the 5 mr and 50 mr scales in parallele
This r
in a 10% deviation (low) it was noticed however that the 10% deviation was not
always forthcoming when the instruemnt was radiation calibrated.
Further study
should reveal use-ful characteristic information.
The deviation percentage given on the cards in the instruments pertains to
Scale error when radiation is read.
COPIED/Do
LANL Re E