Reduce uncertainties in your voltage standard measurements...


The Model 98113 Low Thermal Reversing Switch is a low cost, easy to use device that is designed to mount directly on the output terminals of most commonly used Zener DC voltage reference standards. Its design assures thermal equilibrium between the Zener reference terminals and the contacts of the switch. Its low thermal reversing action assures that the mean value of forward and reverse measurements is the most accurate possible measurement of the Zener reference voltage. Because of its accuracy, the Model 98113 Low Thermal Reversing Switch is used in the NCSLI Josephson Voltage Standard Inter-laboratory Comparison.

The Model 98113 Switch minimizes thermal emf offset by utilizing an isothermal design. Both input and output conductors are thick copper plates tightly clamped to each other and to the aluminum body of the switch through thin Kapton insulating sheets. The armatures and contacting surfaces are solid silver.


The key advantage is that when mounted directly on the terminals of the device under test (DUT), the Model 98113 Low Thermal Reversing Switch is in thermal equilibrium with the terminals and can detect and eliminate thermal voltage between the DUT and your automated reversing switch. The Model 98113 Low Thermal Reversing Switch is manually operated, and used in conjunction with an automated switch. It is an excellent troubleshooting device when there is a potential problem with your automated reversal measurements. By using the Reversing Switch in these instances on an otherwise automated system you can pinpoint the source of offset voltages and reduce your uncertainties.

Specifications and Features

  • Accommodates terminal spacing of 19 mm to 28.6 mm
  • Fits most dc reference standards
  • Input: 1.5 mm thick, copper lugs
  • Output: TeCu terminals on 19 mm centers
  • Typical Thermal Offset: 3 nV
  • Maximum thermal offset: 10 nV
  • Rotation action: + off – off + off – off
  • Leakage resistance: Greater than 100 GΩ
  • Low thermal offset voltage – less than 3 nV typical
  • Terminal Mounting
  • Isothermal Design

Test Data

Typical dc voltage measurements use an automated scanner to connect the device under test (DUT) to the measurement system and to make forward and reverse measurements. Thermal emf's in the scanner and the wiring between the scanner and the DUT are an uncorrected error in this measurement. In the ideal case these thermal errors are insignificant but in reality they often contribute a significant part of the measurement uncertainty. The HPD Model 98113 Switch greatly reduces this uncertainty. Figure 1 shows two sets of measurements of a short circuit made with a scanner only and with the scanner in combination with the 98113 reversing switch. Points on the left side of the figure are the mean value of forward and reverse measurements using only the scanner to reverse polarity. Points on the right side of the graph show the improvement from using HPD Model 98113 switch.

Even better performance is obtained when the Model 98113 is used as the only switch in the measurement but this method may be too labor intensive for calibration laboratories with a large work load.


Price/Quote available upon request.

HPD Model 98113 Low Thermal Reversing Switch
HPD Model 98113 Low Thermal Chart
Contact an HPD sales engineer for more information...
High Precision Devices, Inc.
4601 Nautilus Ct S Boulder, CO 80301 USA
Phone: +1-303-447-2558 Email: