8508A
Users Manual
The Rtp is the resistance of the probe at the triple point of water. For a probe calibrated
for the subrange W7 the coefficient
a+ is equivalent to a
7
, coefficient b+ is equivalent to
b
7
, and c+ to c
7
. Similarly for a probe calibrated for the subrange W4 the coefficient a- is
equivalent to
a
4
, and b- to b
4
. Other subrange coefficients can be substituted for W4 and
W7 coefficients. Unused coefficients should be defaulted to 0.
A similar group of menus appear for the cvd-A conversion and for the cvd-dflt
conversion only the Ro menu appears.
On entry of the final coefficient a check is made against limits for correct algorithm
operation. A message is displayed indicating the coefficients in error. Coefficient values
are not updated.
Measuring Temperature
Connect the PRT or SPRT probe to the multimeter in the same way as when making
resistance measurements, using the appropriate connection shown in figure 3-11. The
corresponding 2, 3, or 4-wire measurement configuration will be automatically set based
on the stored probe characteristics for the probe selection made. Selection of Ex Gd is
recommended.
Note:
Any input zero operations required must be performed in the resistance
function on the 200
Ω
LoI
Ω
and 2 k
Ω
Normal
Ω
ranges prior to entering the
PRT function. Input zeros must be performed in both 2-wire and 4-wire
resistance modes when using the 3-wire PRT configuration.
4-Wire
3-Wire
2-Wire
adj131f.eps
Figure 3-11. PRT Connections
3-28
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