iET PRS-300 Series, Руководство по эксплуатации, Страница: 14 / 50

SPECIFICATIONS
PRS-300 Series
4
2.2 General Specifi cations and Stability
Warmup:
This unit utilizes custom designed low
thermal emf relays for high stability and low-
level signal applications. This thermal voltage
is nominally less than 15
μ
V under laboratory
conditions. Please note that a change in this
thermal emf will give a false drift in resistance
as measured by a dc ohmmeter, since the ohm-
meter will interpret this emf as an effective
resistance. The worst case such effective drift
after warm-up is less than ±25 ppm, primar-
ily due to stabilization of this emf at the relay
contacts as settings are changed.
Unit should be allowed to stabilize for
one hour. For maximum stability, allow unit to
warm-up over two hours.
Recommended Calibration Interval:
Typical calibration interval 12 months.
Adjustment can easily be accomplished us-
ing IET’s PRS-DMM software. Adjusting the
PRS-300 can improve accuracy.
Environmental:
This product complies with the WEEE
Directive (2002/96/EC) marking
requirements. The af
fi xed label
indicates that you must not discard this
electrical/electronic product in domestic
household waste.
Product Category: With reference to the
equipment types in the WEEE Directive Annex
I, this product is classed as a “Monitoring and
Control instrumentation” product.
Effects of Humidity:
Exposure to humidity >60% for a periods
of weeks can cause the resistors to drift some
of which is reversible. It is recommended that
the PRS-300 be stored at humidities less than
50% to minimize this.
More information of the effects of humid-
ity on foil resistors can be found at:
http://www.vishaypg.com/docs/63516/VFR_
TN110.pdf
Short-term Stability:
The PRS-300 was tested for extended pe-
riods of time. Based upon this testing the fol-
lowing stability information was determined.
These speci
fi cations apply for the PRS-300 in
4 terminal mode with shorting links removed
and without switching to another value.
Typical short-term stability without switch-
ing:
< ±(4 ppm + 100 μΩ ) / 10 minutes
Typical 24 hr. Accuracy after Adjustment:
After performing an adjustment per 8.1.4
using a Fluke 8508A and then performing a
calibration veri
fi cation per 8.1.3 within 24
hours the typical accuracy is:
±(30 ppm + 300 μΩ ) for values less than 1 M Ω
±60 ppm for values of 1 M Ω and higher
See graph below for actual performance with 6
digit resolution across resistance range.