Extensometers for materials testing

High Temperature Furnace COD Gages (1200 °C or 1600 °C) – Model 3548COD

High temperature COD gages for use in split type materials testing furnaces with a slot for the ceramic rods. Water-cooled and furnace bracket mounted, these extensometers are for use to 1200 °C (2200 °F). The high temperature option allows use to 1600 °C (2900 °F). They are specifically designed for fracture mechanics testing.

36 EXTENSOMETER MODELS are available in many thousands of variations. Our focus on helping customers has led to the development of models to cover nearly any test method.

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 COD gages mount on a water-cooled bracket, which is mounted on the furnace side cut-out or with optional load frame support brackets. 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. Mounting brackets may be integrated with the furnace cut-out. Epsilon can also provide optional load frame mounting brackets to fit your test frame. Contact edges on the test sample should be somewhat rounded (not sharp knife edges) for best performance with this model.

The Model 3548COD extensometers are strain gaged devices, making them compatible with any electronics designed for strain gaged transducers. Most often they are connected to a test machine controller. The signal conditioning electronics for the extensometer is typically included with the test machine controller or may often be added. In this case the extensometer is shipped with the proper connector and wiring to plug directly into the electronics. For systems lacking the required electronics, Epsilon can provide a variety of solutions, allowing the extensometer output to be connected to data acquisition boards, chart recorders or other equipment.

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  • May be left on through specimen failure.
  • Full bridge, 350 ohm strain gaged design for compatibility with nearly any test system.
  • All standard units meet existing ASTM E1820 requirements for accuracy. A test certificate is included.
  • For KIC/JIC testing, maximum accuracy is achieved with the smallest measuring range and the largest gauge length that will perform the test.
  • All units come with either high purity alumina ceramic rods (1200 °C) or alpha grade silicon carbide rods (1600 °C).
  • Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
  • Rugged, dual flexure design for strength and improved performance.
  • Includes high quality foam lined case and a spare set of ceramic rods.

Download Data Sheet


Excitation: 5 to 10 VDC recommended, 12 VDC or VAC max.

Output: 2 to 4 mV/V, nominal, depending on model

Linearity: ≤0.15% of full scale measuring range, depending on model

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

Operating Force: 30 g typical



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  • Load frame mounting brackets
  • High temperature option (-HT suffix) for use to 1600°C
  • Connectors to interface to nearly any brand of of test equipment

Download Data Sheet


Ordering Information

Click table options to configure

Gauge Length

mm or inches #
5.0 mm -005M 005M
8.0 mm -008M 008M
10.0 mm -010M 010M
12.0 mm -012M 012M
20.0 mm -020M¹ 020M
0.200 in -0020 0020
0.300 in -0030 0030
0.400 in -0040 0040
0.475 in -0047 0047
0.500 in -0050 0050

Measuring Range

extension #
+2.5 mm -025M 025M
+4.0 mm -040M 040M
+7.0 mm -070M 070M
+10.0 mm -100M 100M
+12.0 mm -120M 120M
+0.100 in -100T 100T
+0.150 in -150T 150T
+0.200 in -200T 200T
+0.250 in -250T 250T
+0.500 in -500T 500T

Temperature Range

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

Model Number:  3548COD_ _ _ __ _ __ _

Model Number:

3548COD_ _ _ __ _ __ _

Model 3548COD Available Versions: ANY combination of gauge length, measuring range and temperature range listed above is available, except as noted. 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.

¹Only available in small measuring ranges (rod length dependent).

Example: 3548COD-0050-200T-HT: 0.500 inch compressed gauge length, +0.20 inch measuring range, high temperature option (room temperature to 1600 °C (2900 °F))


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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