iET PRS-330 series, Operation Manual, Page: 33 / 67

PRS-330 Series
OPERATION 21
The only item that can be highlighted and
changed is
Reset to Defaults . Pressing ENTER
will allow the user to select YES or NO to reset
all parameters back to default. The only item this
reset does not affect is Calibration data.
3.5 Thermal emf Considerations
The PRS Series uses high-quality, low-emf
components. Thermal emf is primarily attributable
to the temperature difference between the leads
of the relay and the contacts when temperature
is applied to the coil. This emf is of the order of
5
μ V per relay, but is not usually additive. The
typical worst case is <15
μ
V.
If the effect of tens of microvolts is signi fi cant
to your application, connect to the instrument
with low-thermal-emf materials only. Copper
wire and copper alloys are recommended; brass
and steel should be avoided. Tinned copper and
solder are acceptable.
This emf will
not
be re fl ected if an ac measurement
instrument is employed, and can be eliminated
by using a meter with “True Ohm” capability. In
other cases, the emf may represent a very small
component of a dc resistance measurement.
3.6 Environmental Conditions
The PRS is built, calibrated and intended for
use in a laboratory environment with a nominal
ambient temperature near 23
o C. The accuracy
of the unit may be affected when operated in
non-laboratory environments. Always allow the
instrument to stabilize at room temperature after
unpacking or relocating the instrument. Humidity
should be maintained at laboratory conditions and
typically < 50% RH non-condensing to minimize
shifts in resistance.
3.7 Remote Operation
When the PRS is in REMOTE with front panel
locked out an REMOTE indication will be shown
in bottom half of the HOME screen. Pressing
the LOCAL key will switch the PRS-330 back
to local mode.