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. These liquid-cooled COD gages 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.

38 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.

Model 3548COD mounts on a cooled manifold, which is mounted on an optional load frame mounting system from Epsilon or your furnace’s side cut-out. Epsilon can provide load frame mounting brackets to fit nearly any test frame.

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. Contact edges on the test sample should be somewhat rounded (not sharp knife edges) for best performance with this model.

Model 3548COD gages 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 with electronics for a strain channel, and Epsilon will equip the extensometer with a compatible connector wired to plug directly into the controller. For systems lacking the required electronics, Epsilon can provide a variety of signal conditioning solutions that enable connecting to data acquisition systems 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.
  • 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.

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

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

Accuracy: Standard configurations meet existing ASTM E1820 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, 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

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

Operating Force: 30 g typical



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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

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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