High Temperature Clip-On Gages (700 °C) – Model 7641

Designed for fracture mechanics testing in environmental chambers where the entire gage must be exposed to elevated temperatures. These capacitive sensors may be used up to 700 °C (1300 °F) without any cooling.

$COD gage for elevated temperature fracture mechanics model 7641 Gen2 with CT specimen$

Gen2 Product

Epsilon’s 7641 Gen2 COD Gage improvements:

Fit tighter spaces and a wider variety of specimen designs
More creep-resistant, high-temp tip material
Updated groove geometry – extended tips are now standard
Improved overtravel protection & mechanical robustness
New / additional configuration options for fitment in tight spaces
Increased margin for specimen variation

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

These COD gages use a high-temperature capacitive sensor and do not require any cooling. They will operate up to the maximum temperature limit of most environmental chambers used in materials testing. The Model 7641 is ideal for determination of fracture mechanics parameters such as JIC, KIC, R-curve, fatigue crack growth rate (da/dN), and testing to standards such as ISO 12135, ASTM E1820, E399, E647, etc. All units can be displaced slightly in compression for ease of installation.

The COD gage is supplied with the advanced DT6229 controller. The standard output is a 0-10V analog signal, factory calibrated with the COD gage. This system provides a number of functional enhancements including: built in calibration and tare functions, multi-point linearization, analog and digital filters, high speed digital output, and more.

The 7641 is readily interfaced with most existing test controllers or may be directly connected to a data acquisition system, chart recorder, or a PC. The 7641 may be used for strain-controlled tests such as JIC.

The 7641 Gen2 now includes improved overtravel protection. The enhanced mounting tips accommodate even more specimen geometries, while simultaneously improving handheld ergonomics and ease of installation. Additionally, the improved design now comes standard with an attachment point for tethers and/or counterbalances. The Gen2 model maintains the same high-temperature performance, capable of withstanding temperatures up to 700°C (1500°F), and is available in whole-millimeter gauge lengths ranging from 3mm to 12mm with a variety of measuring ranges.

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May be left on through specimen failure.
All standard models are suitable for cyclic testing.
- >10 Hz typical for 5mm GL and larger
- Typically limited by the user’s test apparatus, specimen, and test method
Digital controller and power supply included. Provides high level DC voltage output with low noise. Easily interfaced to test controllers, data acquisition boards and chart recorders.
- Includes high speed analog and digital outputs
- Intuitive web-based user interface for setup, calibration, and data acquisition
- Built-in calibration reference and auto-zero features
- Multiple extensometer calibration files may be loaded for use with one controller
- Multiple temperature-specific calibrations may be stored
- Selectable analog and digital filter options from 2 Hz to 3 kHz
Ships fully calibrated with electronics (traceable to NPL (UK)) with user-specified voltage output.
Mechanical over-travel protection.
Rugged, dual flexure design for strength and improved performance.
Includes high quality foam lined case.

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Analog Output: User specified, ±10V typical, ±10.8V rail

Digital Output: 24 bit high speed Ethernet output with built-in web interface

Accuracy: All standard configurations meet ASTM E1820, ISO 12135, ISO 9513 Class 0.5, and ASTM E399 (up to 3mm) requirements for accuracy

Linearity: 11 point linearization, ≤0.15% FS typical linearity

Resolution: <55 PPM (0.006%FS) RMS @ 4 kHz, <6 PPM (0.0006%FS) @ 100 Hz

Cyclic Testing: Models available for 10-50Hz testing; see Model Selection Table

Analog Filter: Selectable 100 Hz analog and 2 Hz – 3 kHz digital filters

Temperature Range: Ambient to 700 °C (1300 °F). Use up to 800 °C is possible – contact Epsilon for details. Springs may require periodic adjustment or replacement after long-term testing above ~600 °C.

Temperature Sensitivity (Gain): <100 PPM / °C (0.01%FS/°C) typical (see Temperature Sensitivity Compensation)

Sensor Cable: 0.7 m (2.5 ft) tri-axial high temperature cable, plus 1.5 m (5 ft) room temperature extension cable

Output Cable: Flexible 2.4 m (8 ft) analog output cable

Operating Force: 10-50 N typical, depending on model

Environment: Recommended for elevated temperature testing in dry air or inert / non-corrosive gases

Overall Dimensions: Epsilon-model-7641-Gen2-outline-drawing.pdf

Power: Includes power supply

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Connectors to interface to nearly any brand of test equipment
Bulkhead adapters for vacuum chambers
Bolt on knife edges for attachment to test specimens without machined attachment points

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Storage case (model 7642 shown)

Ordering Information

Click table options to configure

Gauge Lengths

Gauge Length	Model
3.0 mm(0.12in)	-030M	030M
4.0 mm(0.16in)	-040M	040M
5.0 mm(0.20in)	-050M	050M
6.0 mm(0.24in)	-060M	060M
7.0 mm(0.28in)	-070M	070M
8.0 mm(0.31in)	-080M	080M
9.0 mm(0.35in)	-090M	090M
10.0 mm(0.39in)	-100M	100M
11.0 mm(0.43in)	-110M	110M
12.0 mm(0.47in)	-120M	120M

Installed Gauge Length is set by your specimen. Round DOWN to the nearest available size.

Measuring Ranges

Measuring Range	Model	Total Length
5.5 mm(0.22in)	-055MV¹	47.6mm(1.88in)	055MV
7.0 mm(0.28in)	-070MV²	56.5mm(2.23in)	070MV
8.0 mm(0.31in)	-080MV	60.3mm(2.38in)	080MV
9.0 mm(0.35in)	-090MV	66.7mm(2.63in)	090MV
3.5 mm(0.14in)	-035MA¹*	51.1mm(2.01in)	035MA
4.5 mm(0.18in)	-045MA²*	59.9mm(2.36in)	045MA
5.0 mm(0.20in)	-050MA*	63.8mm(2.51in)	050MA
5.5 mm(0.22in)	-055MA*	70.1mm(2.76in)	055MA

* -xxxMA = angled cable exit

¹Best dynamics and stability; recommended for front face specimens
²Good dynamics and stability; best ergonomics; recommended for load line specimens

7641 Clearance Considerations

Epsilon model 7641 Gen2 cable angle and clearance

7641 Total Length and Ergonomics

Model Number: 7641 – _ _ _ _ – _ _ _ _

Model Number:

7641 – _ _ _ _ – _ _ _ _

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Model 7641 Available Versions: ANY combination of gauge length and measuring listed above is available, except as noted. Other configurations may be available with special order; please contact Epsilon to discuss your requirements.

Example: 7641-010M-055MV: 10.0 mm gauge length, +5.5 mm measuring range, vertical cable exit

1. Make sure that model 7641 fits your specimens, grips, and chamber/furnace

Follow these steps: pick a gauge length, pick a measuring range, and check to make sure that the model 7641 configuration you selected fits your specimen, grips, and chamber/furnace. Use these resources: