The Wallace Compression Stress Relaxometer Mk V - C11 | Wallace Instruments
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The Wallace Compression Stress Relaxometer Mk V - C11

General Information

The Wallace Compression Stress Relaxometer (WAC11) allows the operator to easily measure the Compression Stress Relaxation (CSR) characteristics of elastomers and rubber products (e.g. seals, O-rings) as required by the relevant standards.

CSR is a measure of the ability of an elastomer to seal efficiently when held in compression over time and in varying environmental conditions between two rigid faces. The stress at the interface between the elastomer and the rigid faces is important for efficient sealing and is a function of the modulus of the elastomer and the strain applied.

CSR is used by industries including aerospace, automotive and construction to understand the characteristics of elastomeric seals.  Seals are used in numerous applications e.g. O-rings in pipe joints or seals in aero and automotive engines. For safety, warranty and product liability reasons, it is essential that these components, whilst under compression, operate without failure for many years.

The principle of the WAC11 is based on the electrical contact being made between the load cell and the head of the jig. The contact is only broken when the force applied to the Relaxometer marginally exceeds the counterforce exerted by the test sample. The Relaxometer features a ballscrew-driven motorised test frame and load cell designed to apply and measure the required force. At the start of the test cycle the measuring head moves quickly to the jig. At a pre-set position, the measuring head reduces the speed to allow the load cell to more accurately read the force. When the applied force just exceeds the counterforce, the results are displayed graphically and can be saved to a designated folder.

The test sample is compressed by a known amount in a Wallace Test Jig, The resulting force, at the interface between the sample and the jig, is measured using the WAC11 Compression Stress Relaxometer. The WAC11 is easy to use with a simple onscreen operator interface, allowing the test to be initiated quickly and simply. The force is measured at periodic intervals defined by the relevant standards, and the results are displayed on the computer and stored.

Download the Compression Stress Relaxometer Mk V datasheet


The Wallace Compression Stress Relaxometer has the following features:

  • Accurate, repeatable and reproducible measurement
  • Software allows the brakeforce data from a number of individual jigs to be collected and stored
  • Discontinuous method, only one instrument for any number of jigs
  • This WAC11 is backwards compatible with jigs used on previous models
  • Compression force from 0N to a capacity of 2.2kN (500 lbf)
  • Units of measurements mN, daN, N, kN, gf, kgf, ozf, lbf
  • Alternative Load Cell range available


  • Test Jigs made to required sample height/compression percentage - WAC11/1 fixed height or a WAC11/6 adjustable height jig.


The software allows the brakeforce data from a number of individual jigs to be collected and stored.

  • Windows based, easy-to-use software with almost limitless freedom to design and customise compression tests to suit your needs.


See the table below for a run-down of this product's specifications.

Overall Dimensions

941mm (h) x 290mm (w) x 414mm (d)

Weight of Instrument


Max. Power Requirements



230VAC 50Hz or 110VAC 60Hz

Available Load Cell Ranges

2 to 50,000 N

0.2 to 55,000 kgf

0.45 to 11,000 lbf

Load Cell Accuracy

±0.1% of full scale 2 to 2.5kN ±0.2%

Load Cell Resolution


Speed Range 1-1000mm/min

Digital Display of Load/Position/Speed



Operating Temperature

10°C to 35°C

Humidity Range

Normal industry and laboratory conditions

Output of Test Results to PC/Printer/Datalogger

Via USB/networks ports

RS232 via USB converter in ASCII format


Product range

SKU Name Add to quote
WAC11 The Wallace Compression Stress Relaxometer Mk V - C11


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