User`s guide

127
Chapter 4 Features and Functions
Temperature Measurement Configuration
4
RTD Measurements
To connect an RTD to the module’s screw terminals, see page 28.
• The instrument supports RTDs with  = 0.00385 (DIN / IEC 751)
using ITS-90 software conversions or  = 0.00391 using IPTS-68
software conversions. The default is
 = 0.00385.
• The resistance of an RTD is nominal at 0 °C and is referred to as R
0
.
The instrument can measure RTDs with R
0
values from 49 to
2.1 k. The default is R
0
= 100.
• “PT100” is a special label that is sometimes used to refer to an RTD
with  = 0.00385 and R
0
= 100.
• You can measure RTDs using a 2-wire or 4-wire measurement
method. The 4-wire method provides the most accurate way to
measure small resistances. Connection lead resistance is
automatically removed using the 4-wire method.
• For 4-wire RTD measurements, the instrument automatically pairs
channel n with channel n+10 (34901A) or n+8 (34902A) to provide the
source and sense connections. For example, make the source
connections to the HI and LO terminals on channel 2 and the sense
connections to the HI and LO terminals on channel 12.
• Front-Panel Operation: To select the 2-wire or 4-wire RTD function
for the active channel, choose the following items.
TEMPERATURE , RTD , RTD 4W
To select the nominal resistance (R
0
) for the active channel, choose
the following item.
R
o
:100.000,0 OHM
To select the RTD type ( = 0.00385 or 0.00391) for the active
channel, choose the following item.
ALPHA 0.00385
34970A Refresh UG.book Page 127 Wednesday, February 17, 2010 12:34 PM