Key Features

The PRS-330 is the decade resistor you need for calibration labs and automated production environments

Very tight accuracy, almost no long term maintenance costs

  • Resistance range: 0.1 Ω to 20 MΩ with a Resolution of 1 μΩ or 6 digits
  • Lab grade accuracy (70 ppm + 1 mΩ): 1.5 times better than conventual manual decade resistors
  • Large color touchscreen, soft keys and intuitive interface promotes little to no training
  • Can be used as both a Manual or an Programmable unit in both calibration lab and production environments.
  • Comes standard with USB, Ethernet and IEEE interfaces and full LabView command structure, see manual and drivers for more details
  • If you do NOT own an 8.5 Digit DMM (Fluke 8508A or Keysight 3458) OR if you require an Ethernet or USB Interface this is the instrument for you
  • Virtually no maintenance cost, very simple to calibrate. If it drifts, it easily adjusts back to spec without costly repairs
  • High reliability relays, rated for 100 Million Switches
  • Rated for use at 0.5 W, for higher power consider the PRS-202
  • Use for RTD applications is straightforward with built-in PT-100 and PT-1000 Tables, RTD values can be input in both °C, °F
  • Strong ac performance
  • No zero or switch resistance 0.1 Ω is 0.1 Ω
  • Front and rear binding posts for ease of connection
  • Sold with an industry leading 5 year warranty and Manufactured in the USA
  • About 10% lower in cost than the PRS-370 or its predecessor unit the PRS-300
  • If you already own, or are considering buying, an 8.5 Digit DMM you should strongly consider the PRS-370 instead of the 330


The PRS-330 was designed with the right mix of features for to be efficient for both manual and automated application in both laboratory and production environments such as; calibration of resistance meters, calibration of temperature controllers and indicators, automated test systems requiring a precision resistive load.

With its wide resistance range and 6-digit resolution, the PRS-330 was designed to replace multiple decade boxes and reduce test time.

With its industry leading 5-year warranty all aspects of the PRS-330 focus on reliability, reduced ownership costs and simplicity out of the box.

User interface
The PRS-330 utilizes a large state-of-the-art color capacitive touchscreen which provides super-fast response time. Even in low or bright light conditions, the display provides exceptional clarity with large fonts and easy-to-read menus.
The user interface also features softkeys and a numeric keypad allowing the use of the user interface without using the touchscreen.

Interface and drivers
The operation is both local using a color touch screen, soft keys, and numeric keypad or remote control with standard USB, Ethernet, and IEEE-488 interfaces. The versatility of USB, Ethernet or GPIB interfaces allows you to completely automate your testing.

Highest quality components
The programmable resistance box employs high-quality gold-plated tellurium-copper five-way binding posts serve to minimize the thermal emf effects, which would produce errors in dc resistance measurements. Resistors are custom Z-foil and low inductance wirewound for low TC and excellent stability.

RTD calibration
Built-in tables for PT100 and PT1000 RTDs and direct resistance substitution makes the PRS-330 ideal for RTD (Resistance Temperature Detector) simulation. User-defined tables can also be created for use with other RTDs. The operator can enter temperature directly and the correct resistance will automatically be programmed.

No zero resistance. 0.1 Ω is 0.1 Ω
The PRS Series programmable resistance box employs very low resistance, low thermal emf relays with gold-clad silver-alloy contacts. A special design keeps contact resistance to a minimum. The gold plating keeps the silver contacts from becoming tarnished when unused, or when only low currents are passed through them. This is most often the case when only minute test currents are drawn by digital multimeters and other test instruments. Contact resistance remains low and repeatable through the use of multiple contacts.

Switching between resistance changes
The relays can be switched via fast, short or open. Fast switching changes resistance values with a switch time of less than 10 ms. Short and open allows a known state when resistance values are changed either manually or programmatically however more time is required between switching. Short switching introduces a short (0.1 Ω) in between resistance changes. Open switching introduces an open between resistance changes.

ac performance
The PRS-330 programmable resistance box is a precision resistance source with excellent characteristics of stability, temperature coefficient, and power coefficient. The use of low inductance wirewound and Z-foil resistors allows the PRS-330 to be used in ac applications with minimal resistance change below 1 kHz.
See PRS Decade Resistor ac Performance Application Note for additional information.

Resistor carousel
Built-in EIA “preferred value” resistance tables of 1% (E96), 5% (E24), 10% (E12) increments or user specified increment allows the PRS-330 to be used as a resistor carousel.

Further improve on accuracy to <15 ppm
Additionally, if you own an 8.5 digit DMM, Fluke 8508A, 8588A or the Keysight 3458A, for no additional cost, the PRS-330 can be used as part of the PRS-DMM system which will further improve on the accuracy of the unit to However, unlike the PRS-370 this requires a separate PC for operation.


If you own or consider buying one of these DMM’s you should strongly consider the PRS-370 instead of the PRS-330

The Patented PRS-370 Programmable Resistance Standard can control an 8.5 digit DMM like Fluke 8508A, 8588A or the Keysight 3458A, and automatically adjust the source resistance to achieve an accuracy of <10 ppm without the need of an external computer

Calibration history
Calibration history of each internal resistor can be reviewed to show drift and performance. The calibration history data can be retrieved via SCPI command for further analysis. Pressing a switch on the front panel allows access to calibration history and adjustment menus minimizing unauthorized access.

Cybersecurity statement
The PRS-330 contains a microcontroller, and runs proprietary firmware. The firmware can only be updated via a JTAG or similar cable and only accessed by removing the top cover of the instrument. There are no facilities to update firmware via the USB, Ethernet or GPIB interfaces on the PRS-330.
Windows or Linux are not used in this product. A factory reset is provided which will reset the PRS-330 back to factory default including calibration data history and all other data that can be saved by a user.

Optional Rack Mounting
The PRS Series programmable resistance box may be rack mounted to serve as components in measurement and control systems.

USB driver for Windows 7 and Windows 10
The USB interface uses a MCP2200 Driver. If the driver is not automatically installed by Windows this can be download and installed using the link below.
For USB interface: Download:
Unzip the file and follow instructions to install.

Ethernet interface
For Ethernet interface: Download:
Unzip the file and follow instructions to install. The application allows the user to change IP address and communicate with the PRS. Please see PRS-330 instruction manual for more information.

Related Products


  • Resistance Range: 0.1 Ω to 20 MΩ
  • Precision Lab Grade Accuracy 70 ppm + 1 mΩ
  • Resolution: 1 μΩ ( 0.000 001 Ω) or 6 digits
  • To further improve accuracy to <20 ppm, for no additional cost, see the PRS-DMM
  • Programmable resistor with USB interface and Labview drivers
  • 5 year warranty


  • 8 Resistances from 10 kΩ to 5 MΩ standard
  • Standard accuracy: ±10% at 23°C
  • Power rating : up to 300 W at 100 kΩ
  • Voltage rating: 1,400 to 5,500 V depending upon resistance value
  • Continuous operation at rated power
  • Kel-F washers on all terminals for low leakage current and high dielectric strength
  • Custom values available for AR and QuadTech/Chroma hipot testers


  • High accuracy – 20 ppm + 0.5 mΩ
  • High stability – 20 ppm + 0.5 mΩ
  • Resistance from 10 mΩ to 1.1 MΩ
  • 20 μΩ resolution
  • Precise fixed minimum resistance
  • Hermetically sealed, low inductance resistors
  • The first 4 decades can be individually trimmed for increase accuracy


  • Precision accuracy of ±(0.01% + 2 mΩ)
  • Resistance range from 0.01 Ω to 11.1111 MΩ
  • 4 models available, each covering six decades
  • High-performance solid silver-alloy contacts
  • Low zero resistance < 6mΩ


  • Resistance Values 1 MΩ & 10 MΩ
  • Initial Accuracy… ± 25 or 30 ppm of nominal value matched within 10 ppm
  • Transfer Accuracy… ± 2 ppm (Typical Short-term Repeatability)
  • Calibration Accuracy… ± 10 or 15 ppm


  • Resistance Transfer Standards available in the following values 1 Ω, 10 Ω, 100 Ω, 1 kΩ, 10 kΩ, 100 kΩ
  • Initial Accuracy… ± 20PPM of nominal value matched within 10PPM
  • Transfer Accuracy… ± (1PPM + 0.1uΩ at parallel value) for 100:1
  • Transfer Accuracy… ± (1PPM + 1uΩ at series parallel value) for 10:1
  • Long Term Accuracy… ± 50PPM of nominal value
  • Calibration Accuracy… ± 10PPM


  • IEEE, RS232 or Ethernet Programmable Decade Resistor
  • Wide range and resolution: 100 mΩ to 100 M&Omega with 1 mΩ resolution
  • Available at accuracies of : 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, and 1%
  • Special RTD and custom configurations
  • Dual / Combo rackmount models ( examples: Resistance & Capacitance or Resistance & Inductance)


  • Resistance Values of 1 Ω – 100 kΩ
  • Initial Accuracy… ± 20 PPM of nominal value matched within 10 PPM
  • Transfer Accuracy… ± (1 PPM + 0.1uΩ at parallel value) for 100:1
  • Long Term Accuracy… ± 50 PPM of nominal value
  • Calibration Accuracy… ± 10 PPM