High Temperature, Ultra-Low Contact Force Capacitive Extensometers (1200°C or 1600°C) – Model 3648

This model was designed for applications that require ultra-low contact force when using split type materials testing furnaces or induction heaters. It features very low specimen contact force and includes a slide bracket for mounting. Liquid cooling allows use to 1200°C (2200°F) standard or 1600°C (2900°F) with the high temperature option.

Epsilon extensometers are COMPATIBLE WITH VIRTUALLY EVERY BRAND OF TEST EQUIPMENT and can be supplied with the correct connector to plug in directly.

Operation of these, and all of Epsilon’s extensometers, are


using in-house calibration systems that are calibrated with Epsilon’s laser interferometer system.


to the materials testing community, you know we will be there to stand behind our products when your critical application requires it.

These extensometers use a high temperature capacitive sensor in combination with an innovative design to achieve high accuracy strain measurements in low measuring ranges. They mount on a slide bracket (included) that can attach to the load frame of your test system; optional load frame mounting brackets are available.

The standard temperature version (to 1200 °C) is supplied with high purity alumina rods. The high temperature option is furnished with alpha grade silicon carbide rods. Rods are made to order to the length required for your furnace. These units are made to order in many different gauge lengths and measuring ranges.

The extensometer comes with a signal conditioner. The output is an analog DC voltage, factory calibrated with the extensometer to 0 to ±10 VDC typically. They are readily interfaced with most existing test controllers and may be directly connected to data acquisition systems. Bringing the signal into a spare DC input channel (or external input) on the test controller allows the extensometer to be used for strain controlled tests like low cycle fatigue.

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  • May be left on through specimen failure.
  • Designed for applications requiring ultra-low contacting force with a measuring range less than ±2.5 mm (±0.10 inches). Epsilon recommends Model 3549 or Model 7650A for most applications..
  • Capacitive signal conditioner and power supply included. Provides high level DC voltage output with low noise. Easily interfaced to test controllers, data acquisition boards and chart recorders.
  • Hot mountable and retractable.
  • Shipped fully calibrated with electronics (traceable to NPL (UK)) with user specified voltage output.
  • All models can measure in both tension and compression and can be used for cyclic testing.
  • Mechanical overtravel stops in both directions.
  • Innovative slide mount allows the extensometer to engage the specimen once the test temperature has been achieved.
  • Includes high quality foam lined case and a spare set of ceramic rods.

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Output: User specified, +/-5 VDC or +/-10 VDC typical

Accuracy: Standard configurations meet ASTM E83 class B-1 and ISO 9513 class 0,5 requirements for accuracy. A test certificate is included. Rod lengths >250 mm (10″) can affect the final class rating.

Linearity: ≤0.15% of full scale measuring range (rod length dependent)

Temperature Range: Standard (-ST) is to 1200 °C (2200 °F), optional (-HT) 1600 °C (2900 °F)

Cable: Integral, ultra-flexible cable, 2.5 m (8 ft) standard

Coolant Interface: Two barbed hose fittings for 1/8” (3.2 mm) ID coolant hoses

Contact Force: Adjustable up to 150 g (30-50 g typically used)

Operating Force: <10 g typical

Power: Includes power supply for your country (specify)

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  • Model EPS170 constant-temperature recirculating chiller
    Liquid cooling is recommended for all elevated temperature tests to obtain the best measurement accuracy and retain the validity of a room temperature calibration when the specimen temperature is >540 °C (1000 °F). Cooling is necessary to prevent extensometer damage for testing in the range of ~800-1600 °C (1500-2900 °F). Epsilon Technology recommends the EPS170 constant-temperature recirculating chiller.
  • High temperature option (-HT suffix) for use to 1600°C
  • Load frame mounting brackets
  • Connectors to interface to nearly any brand of test equipment
  • Rod tips can be straight chisels or conical tips; specify when ordering
  • VREF Module

Download Data Sheet

Ordering Information

Click table options to configure

Gauge Length i

mm or inches #
10.0 mm -010M 010M
12.5 mm -0125M 0125M
25.0 mm -025M 025M
50.0 mm -050M 050M
0.500 in -0050 0050
1.000 in -0100 0100
2.000 in -0200 0200

Measuring Range i

extension #  
±0.5 mm -005M 005M
±1.0 mm -010M 010M
±2.5 mm -025M 025M
±0.020″ -020T 020T
±0.040″ -040T 040T
±0.100″ -100T 100T

Temperature Range

degrees #
Ambient to 1200 ˚C (RT to 2200 ˚F) -ST ST
Ambient to 1600 ˚C (RT to 2900 ˚F) -HT HT

Model Number:  3648_ _ _ __ _ __ _

Model Number:

3648_ _ _ __ _ __ _

Model 3648 Available Versions: ANY combination of gauge length and measuring range listed above is available, except as noted. Contact Epsilon for additional gauge length options. Ceramic rod lengths are made to fit furnaces as required. Please provide furnace dimensions at the time of order. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

Example: 3648-025M-010M-ST: 25.0 mm gauge length, ±1.0 mm (±4.0 % strain) measuring range, standard temperature option (room temperature to 1200 °C)


If your unit is in need of service, calibration or repair, initiate the RMA process with us and we will be happy to assist.

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