*TB 43-177
Vxi = Vref + vi + tc
a. Temperature corrections must be computed for
both the reference and working group when the
th
Where Vxi is the computed voltage value for the i
temperatures of the enclosures at the time of test are
cell in the working group; Vref is the certified mean
different from their nominal temperatures.
These
voltage of the reference standard cell group at nominal
corrections may be closely approximated by the following
temperature, vi is the measured differences (small
equation.
between cells obtained from the measurement design,
Tc = ∆t Ct
and tc is the net temperature correction for both the
reference and working enclosures.
Where:
Tc is the temperature correction
∆t is the actual temperature minus
B-5.
The measured data from the observation sheet
nominal temperature
is substituted into the following equations to obtain the
Ct is the temperature coefficient
value for each cell of the working group at nominal
at the nominal temperature
temperature:
The most common nominal temperatures for standard
(obs) + (obs10) - (obs1) - (obs2) + tc
cell maintenance are 28C, 30C, 32C, and 35C.
Cell A =V ref +
Temperature coefficients at these temperatures are
4
given below.
V ref + (obs11) + (obs12) - (obs3) - (obs4) + tc
Cell B =
C28 = -54 V/C
4
C30 = -57 V/C
C32 = -59V/C
V ref + (obs13) = (obs14) - (obs5) - (obs6) + tc
Cell C =
C35 = -62 V/C
4
V ref + (obs15) + (obs16) - (obs7) - (obs8) + tc
b. For an example, consider the data in figure B-
Cell D =
1. Nominal temperature of the transport standard is
4
32C. Measured temperature is 32.004C.
Vx (Mean of UUT Group) =
Tc = ∆t Ct
Then
(cell A)+(cell B)+(cell C)+(cell D)
Tct = .004 x (-59)
4
Tct = -.236 V for the transport standard
B-6.
To obtain the value for each cell of the
Nominal temperature of the lab standard is 32C.
reference group, substitute the measured data from the
Measured temperature is 32.009C.
V x from 4 above into the
observation sheet and
following equations:
Tcl = ∆t Ct
Then
Tcl = .009 x (-59)
Tcl = -.531 V for the lab standard
V x + (obs 1)+(obs 8)-(obs 12)-(obs 13) -tc
Cell 1 =
4
c. The correction tc used in this technical bulletin
corrects voltages to the nominal temperature of both
V x + (obs 2)+(obs 3)-(obs 14)-(obs 15) -tc
Cell 2 =
enclosures and is computed as follows:
4
tc = Tct - Tcl
V x + (obs 4)+(obs 5)-(obs 9)-(obs 16) -tc
Cell 3 =
For this example:
4
tc = -.236 - (-.531)
tc = +.295 V
V x + (obs 6)+(obs 7)-(obs 10)-(obs 11) -tc
Cell 4 =
4
This is the quantity that would be substituted in the
B-7. Temperature Corrections
equation (B-4 above) for tc.
B-8.
Sample computations for the data in figure B-1.
B-3
