High Temperature, Low Strain Capacitive Extensometers (1200°C or 1600°C) – Model 3648

  • These extensometers use a high temperature capacitive sensor in combination with an innovative design to achieve high accuracy strain measurements in low measuring ranges not possible with other high temperature extensometers. 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 overall design reduces any influence from common lab environment vibrations.

    The standard temperature version (to 1200℃) 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 and chart recorders. 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.


  • • May be left on through specimen failure.

    • Hot mountable and retractable.

    • Designed for those applications requiring ±2.5 mm (±0.10 inches) full scale measuring range or less. For applications requiring greater measuring ranges, see Model 3549 (page 26).

    • A signal conditioner and power supply included. Provides high level DC voltage output with exceptionally low noise (typical 0.1 mV on 10VDC output). Easily interfaced to test controllers, data acquisition boards, and chart recorders.

    • Hot mountable and retractable.

    • Shipped fully calibrated with electronics (traceable to NPL) 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.

    • Standard units meet ASTM class B-1 requirements for accuracy. A test certificate is included. ISO 9513 class 0,5 test certificates are available upon request.

    • Includes high quality foam lined case and a spare set of ceramic rods.

    • Innovative slide mount allows the extensometer to engage the specimen once the test temperature has been achieved.

    • Low strain range, high resolution versions available. 


  • Model 2050 constant temperature water re-circulating bath

    High temperature option (-HT suffix) for use to 1600℃ 

    Load frame mounting brackets

    Specify rod tip style desired. Available choice are:

    Straight chisel, vee chisel, conical tip 


  • Input: Includes power supply for your country (specify)

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

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

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

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

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

    Operating Force: <10 g typical 


This model was designed for low strain applications for use with split type materials testing furnaces or induction heaters. It features very low specimen contact force and includes a slide bracket for mounting. Water cooling allows use to 1200℃ (2200°F) standard or 1600℃ (2900°F) with the high temperature option.
Gauge Lengths:
10-50 mm
Measuring Ranges:
Up to ±2.5 mm
Temperature Range:
Ambient to 1600℃ with -HT option
Key Features:
Hot-mountable, low strain furnace extensometer