The HARS-LX series is the world's highest accuracy continously variable
decade resistor for the most exacting calibration and test applications.
- High accuracy - as good as 20 ppm
- High stability - as good as 5 ppm/yr
- Over 55 models available with resistance from 1 mΩ to 121.1 MΩ
- Resolution as good 1 mΩ with a fixed decade or 100 μΩ with a rheostat.
- Low temperature coefficient - as low as 3 ppm/°C
- High performance solid silver contact switches
- Hermetically sealed, low inductance resistors
- No zero correction required
- For increased accuracy, decades ≥ 1 Ω can be individually trimmed
- The US Army's Resistance Standard
The HARS-LX substituter is a
precision resistance source with excellent characteristics of accuracy,
stability, temperature coefficient, and power coefficient. All these features
serve to make it a laboratory resistance standard, exceeded in performance only
by stand-alone standard resistors.
Hermetically sealed wirewound
resistors are used for 1 Ω steps and over. These resistors are carefully
conditioned under power and temperature in order to develop the best stability
characteristics. Actual experience has shown them to exhibit a storage stability
of better than 5 ppm/year, improving as they age. The low-resistance resistors
are constructed with resistance wire with a minimum of copper resistance in
series to limit temperature coefficient effects.
The resistance
substituuter has a fixed minimum resistance of 10 mΩ. This is implemented by
mechanically limiting the 10 mΩ decade from going below the “1” position. In
this manner, no zero resistance subtractions have to be made, and the accuracy
given is for the absolute reading.
The HARS-LX series employs completely
enclosed dust-tight very low contact resistance switches. They feature solid
silver alloy contacts and quadruple-leaf silver alloy wipers which keep switch
contact resistance to under 1 mΩ per decade, and more importantly, keep switch
contact resistance reproducible, insuring repeatable instrument
performance.
High quality gold plated tellurium copper binding posts
minimize the thermal emf effects which would artificially reflect a change in dc
resistance measurements. All other conductors within the instrument, as well as
the solder employed, contain no metals or junctions that contribute to thermal
emf problems.
The HARS-LX is designed to allow very convenient
maintenance of calibration over time. Most decades are calibratable without
changing components or soldering resistors. The decades for the 100 Ω through
100 kΩ steps are calibrated with convenient trimmers. Trimming of the lower
decades is also possible.
With a resolution as low as 1 mΩ and a maximum
available resistance of over 12.2 MΩ, the HARS-LX Series may be employed for
exacting precision measurement applications requiring high accuracy and
stability. They can be used as components of dc and low frequency ac bridges,
for calibration, as transfer standards, and as RTD simulators.
HARS-LX BASIC SPECIFICATIONS
|
Resistance per step |
Total decade resistance |
Max current |
Max power |
Temperature coefficient (ppm/ºC) |
Power coefficient (ppm/mW) |
Accuracy |
Stability(±}ppm/yr |
|
100μΩ Rheostat |
10 mΩ |
2 A |
NA |
20 |
1 |
|
|
|
1 mΩ |
10 mΩ |
2 A |
NA |
20 |
1 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
10 mΩ |
100 mΩ |
2 A |
NA |
20 |
1 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
100 mΩ |
1 Ω |
2 A |
NA |
20 |
1 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
1 Ω |
10 Ω |
1 A |
5 W |
20 |
0.4 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
10 Ω |
100 Ω |
0.33 A |
5 W |
10 |
0.3 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
100 Ω |
1 kΩ |
0.1 A |
5 W |
3 |
0.1 |
20 ppm+0.5 mΩ |
20 ppm+0.5 mΩ |
|
1 kΩ |
10 kΩ |
33 mA |
5 W |
3 |
0.1 |
20 ppm+0.5 mΩ |
10 ppm(<5 ppm typical) |
|
10 kΩ |
100 kΩ |
10 mA |
5 W |
3 |
0.1 |
20 ppm+0.5 mΩ |
10 ppm(<5 ppm typical) |
|
100 kΩ |
1 MΩ |
3 mA |
2,000 V |
3 |
0.1 |
20 ppm+0.5 mΩ |
10 ppm(<5 ppm typical) |
|
1 MΩ |
10 MΩ |
1 mA |
2,000 V peak |
3 |
0.1 |
20 ppm+0.5 mΩ |
10 ppm(<5 ppm typical) |
|
10 MΩ |
100 MΩ |
|
2,000 V peak |
15 |
0.2 |
2000 ppm |
50 ppm |
|
Wiring and switch resistance |
|
50μΩ/C |
0.2μΩ/W |
|
|
At 23°C
"true ohm" measurement, 30-70% RH, absolute reading, SI traceable
No zero
subtraction required
Minimum resistance:10 mΩ ± 0.5 mΩ; determined by the
lowest settable position, "1", of the 10 mΩ/step decade
Resistance
repeatability: Better than 100 μΩ, short-term, average value
