2-12 Voltage and Temperature Measurements
Connections
WARNING A hazardous voltage condition exists at or above 42V peak. To prevent
electric shock that could result in injury or death, NEVER make or break
connections while hazardous voltage is present.
CAUTION Exceeding the following limits may cause instrument damage not covered
by the warranty:
• Channel 1 HI and LO inputs have a maximum measurement capability
of 120V peak. These inputs are protected to 150V peak to any terminal
or 350V peak to chassis.
• Channel 2 HI and LO inputs have a maximum measurement capability
of 12V peak. Channel 2 HI is protected to 150V peak to any terminal,
and Channel 2 LO is protected to 70V peak to Channel 1 LO. Both inputs
are protected to 350V peak to chassis.
NOTE As a general rule, use Channel 1 whenever possible to measure voltage below 1V. If
using Channel 2 to measure <1V and the impedance between Channel 2 LO and
Channel 1 LO is >100k
Ω
, pumpout current may be high enough to corrupt
measurements. In this case, the Low Charge Injection mode can be enabled to reduce
pumpout current (at the expense of increased measurement noise). See “Performance
considerations, Pumpout current (low charge injection mode)” for details.
Connection techniques
Copper-to-copper connections should be used wherever possible in the test circuit to
minimize thermal EMFs that could corrupt measurements (see “Measurement error - external
causes” for information on thermal EMFs).
Any solder connections to your test circuit require the use of silver solder to minimize thermal
EMFs. You can order a 20-foot length of silver solder from Keithley (part number 2182-325A).
Included with the solder is an MSDS sheet listing the solder chemical contents.
CAUTION Silver solder has a high temperature melting point. Take care not to damage
a LEMO connector (or any other device) by applying excessive heat.
Model 2107 input cable
The Model 2107 Input Cable, which is a supplied accessory, is terminated with a LEMO con-
nector on one end and copper lugs on the other end. The cable is shielded to chassis ground when
connected to the Model 2182. The cable wires are made from twisted silver wire. The input cable
is shown in Figure 2-2. This cable can be used to make voltage measurements and temperature
measurements that use an external simulated reference junction.
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