IET Labs PRS-370 SERIES, Operation Manual

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MAINTENANCE
PRS-370 Series
30
The PRS-370 consists 43 internal resistors
which are combined in either series or parallel
to achieve the programmed resistance.
These resistors require periodic measurement to
keep the PRS-370 within published speci
fi cations.
The resistors are measured using a DMM. The
measured value is then stored in a table within
the memory of the PRS-370. The measured
values of the resistors are used in an algorithm
to determine which resistors are used to create
the programmed resistance value.
In addition to the 43 resistors the residual
internal lead resistance is also measured at time
of manufacture and entered into memory. The
internal lead resistance does not need to be
measured again unless repair has been performed
to the PRS-370.
Below is a list of the 43 resistors and their
nominal resistance value. These resistors should
be within ±1% of the nominal value for R1 to R5
and ±0.1% of the nominal value for R6 and higher
to ensure proper operation of the PRS-370. If the
measured value of the resistor is outside of these
speci
fi cations service is required.
The Calibration History will show each resistor
value and previous calibrated values so that drift
of the individual resistors can be evaluated.
Resistance
Number
Nominal Resistance
Value
R1 0.17 Ω
R2 0.35 Ω
R3 0.7 Ω
R4 1.37 Ω
R5 2.66 Ω
R6 5.15 Ω
R7 10.2 Ω
R8 20.0 Ω
R9 38.8 Ω
R10 75.6 Ω
R11 148.0 Ω
R12 287.0 Ω
R13 570.0 Ω
R14 1.13 k Ω
R15 2.23 k Ω
R16 4.4 k Ω
R17 8.7 k Ω
R18 17.0 k Ω
R19 33.3 k Ω
R20 66.0 k Ω
R21 130.0 k Ω
R22 258.0 k Ω
R23 506.0 k Ω
R24 1.0 M Ω
R25 2.0 M Ω
R26 3.99 M Ω
R27 7.8 M Ω
R28 15.0 M Ω
R29 30.0 M Ω
R30 60.0 M Ω
R31 120.0 M Ω
R32 3.55 k Ω
R33 7.39 k Ω
R34 16.4 k Ω
R35 33.8 k Ω