Automatic Gauge Length Extensometers – Model 3742

Clip-on extensometers featuring automatic gauge length setting for fast, repeatable mounting to samples — no gauge pins required. Switch gauge lengths in seconds using the new Quick-Swap gauge length system. Built for productivity with high precision.

New Product

CLIP-ON EXTENSOMETERS OFFER MAXIMUM PERFORMANCE

with a minimum price. Prefer the versatility of a non-contact extensometer? Consider Epsilon ONE®.

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

VERIFIED TO APPLICABLE STANDARDS SUCH AS ASTM E83 OR ISO 9513

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

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

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Model 3742’s gauge length is set automatically – saves time.

Change gauge lengths in seconds without tools.

The Model 3742 clip-on extensometer is designed for fast mounting and high testing efficiency. It is ideal for laboratories that require frequent specimen and gauge length changes, reduced setup time, and consistent, repeatable strain measurements. The 3742 is applicable for testing a wide range of materials, including metals, plastics, composites, and ceramics, in both tension and compression.

This model sets the gauge length automatically as the extensometer is mounted on the specimen. Gauge length pins are not required. Gauge lengths can be changed in seconds, without tools, using the 3742’s new Quick Swap gauge length system, and fine adjustments can be made to ensure that the gauge length remains within tolerance. Clamping force is easily adjusted without tools.

The Model 3742 includes Epsilon’s quick attach kit as a standard feature, allowing the extensometer to be mounted quickly and easily.

Model 3742 extensometers are applicable for testing in accordance with the following standards:

ISO 6892-1, 527-2, 527-4, 527-5, 10113
ASTM E8, E9, D3039, D638, A370, D3552, E517, E646

Model 3742 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 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 solutions for signal conditioning and connection to data acquisition systems or other equipment.

For gauge lengths less than 25 mm or 1 inch, Epsilon offers the more compact Model 3442. For gauge lengths between the increments in Model 3742’s gauge length table, see Model 3542. For gauge lengths greater than 100 mm or 4 inches, see Model 3542L. Epsilon ONE non-contacting extensometers will also work with a wide range of gauge lengths.

Download Data Sheet

Automatic gauge length – the gauge length is set automatically when the extensometer is mounted on the specimen, eliminating gauge pins and enabling faster testing.
Change gauge lengths in seconds using the Quick-Swap gauge length system – no tools required.
Gauge length fine-adjust feature makes adjustments quick and easy if an adjustment is required.
Clamping force is easily adjusted without tools.
May be left on through specimen failure in most applications.
p
When does an extensometer have to be removed before specimen failure?

Remove model 3542 and 3442 extensometers before specimen failure, or use an Epsilon ONE® non-contacting extensometer, in the following applications:
- Rebar and other materials with textured or rough surface finishes (note: use model 3543 or Epsilon ONE to test rebar through failure)
- Wire cable
- Unidirectional composites and similar materials that explode / disintegrate at failure
- Non-rigid griping systems such as “lever action” wedge grips with moveable grip faces or grips with spherical seats
- Long samples of elastic material
- When the expected elongation of the material exceeds the extensometer’s measuring range (for example, using a 10% extensometer with a metal specimen that fails at 20% elongation)
- Rupture of internally pressurized specimens
All models can measure in both tension and compression and can be used in closed-loop strain control and for cyclic testing.
Standard Quick Attach Kit allows fast mounting to specimens.
Rugged, dual flexure design for strength and improved performance. Much stronger than single flexure designs, this also allows cyclic testing at higher frequencies.
Includes mechanical overtravel stops in both directions.
Hardened tool steel knife edges are easily replaced. A spare set of standard knife edges and a set of 3-point knife edges come with every model 3742.
High and low temperature options for -270 °C to +200 °C (-454 °F to +400 °F).
Compatible with nearly any test system – full bridge, 350 ohm strain gaged design.
Includes the Epsilon Shunt Calibration System for on-site electrical calibration.
Includes high quality foam lined case.

Download Data Sheet

Specimen Sizes and Attachment:
– Quick Attach Kit wireforms are included for round samples 2-25 mm (0.08-1.0 inch) diameter and flats up to 12 mm thick by 31 mm wide (0.5 inch by 1.25 inch); wireforms are available for many other specimen sizes – contact Epsilon
– Model 3442 is recommended for specimen diameters <2 mm

Accuracy: Meets ASTM E83 class B-1 and ISO 9513 class 0,5 accuracy requirements. A test certificate is included.

Linearity: ≤0.15% of full scale measuring range

Temperature Range: Standard (-ST) is -40 °C to +100 °C (-40 °F to 210 °F); see Ordering Information for additional ranges

Operating Force: Depends on model configuration; 10 to 100 g typical

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

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

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

Download Data Sheet

Quick-Swap gauge lengths
Quick Attach Kit wireforms for larger specimens
Gauge length pin assembly with rubber band and spring attachments for non-ambient testing
Temperature options for -270 °C to +200 °C (-454 °F to +400 °F)
Connectors to interface to nearly any brand of test equipment
Special strain gage coatings and stainless steel knife edges for biomedical testing at room temperature
Specialty Knife Edges

Download Data Sheet

Mounting with 3742's automatic gauge length mechanism
Testing composites; 50mm GL and +12.5mm MR shown
Testing metals; 25mm GL and +25mm MR shown
Testing metals; 50mm GL and +25mm MR shown
Testing plastics; 50mm GL and +12.5mm MR shown
Installing a Quick Swap gauge length system only takes a few seconds

Ordering Information

Click on the tables to select one or more Gauge Lengths, one Measuring Range, and one Temperature Range.

pGauge Length
Selecting Extensometer Gauge Length

Extensometer Gauge Length is the distance between the extensometer’s initial measuring points on the specimen. If you are using a testing standard, check the standard for extensometer gauge length requirements. Many test standards specify the specimen dimensions and a matching extensometer gauge length.

Many specimens have a reduced section length that is designed to be greater than the extensometer’s gauge length.

mm or inches	#
25.0 mm	-025M	025M
30.0 mm	-030M	030M
35.0 mm	-035M	035M
40.0 mm	-040M	040M
45.0 mm	-045M	045M
50.0 mm	-050M	050M
55.0 mm	-055M	055M
60.0 mm	-060M	060M
65.0 mm	-065M	065M
70.0 mm	-070M	070M
75.0 mm	-075M	075M
80.0 mm	-080M	080M
100.0 mm	-100M	100M
1.000 in	-100T	100T
1.400 in	-140T	140T
1.500 in	-150T	150T
2.000 in	-200T	200T
2.500 in	-250T	250T
3.000 in	-300T	300T
4.000 in	-400T	400T

pMeasuring Range
Selecting Extensometer Measuring Range

Measuring Range is the measuring capacity of the extensometer in tension (+) or compression (-) in units of % strain, maximum extension, or maximum deflection. When measuring range is in units of % strain, this means the maximum extension as a percentage of the gauge length.

Estimate the maximum strain or extension values you will need to measure, such as the total strain when the extensometer is removed after offset yield or the elongation at fracture. Then select a measuring range for the extensometer that meets or exceeds the requirements for the materials you are testing. If you are using a testing standard, also check the standard for extensometer requirements.

extension	#
+10.0/-5.0 mm	-1	1
+12.5/-5.0 mm	-2	2
+25.0/-5.0 mm	-3	3
+50.0/-5.0 mm	-4	4
+0.40/-0.20 in	-1	1
+0.50/-0.20 in	-2	2
+1.00/-0.20 in	-3	3
+2.00/-0.20 in	-4	4

Temperature Range

degrees	#
-270 °C to 100 °C (-454 °F to 210 °F)	-LT	LT
-40 °C to 100 °C (-40 °F to 210 °F)	-ST	ST
-40 °C to 150 °C (-40 °F to 300 °F)	-HT1	HT1
-40 °C to 200 °C (-40 °F to 400 °F)	-HT2	HT2
-270 °C to 200 °C (-454 °F to 400 °F)	-LHT	LHT

Model Numbers:
Measuring Range	3742 – _ – _ _
		Tensile Measuring Range
Gauge Length	3742GL – _ _ _ _ – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Gauge Length	3742GL – – _	_ _ _ _
Order one Measuring Range system and one or more Gauge Length systems

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Model 3742 will begin shipping on 13 October 2025. After that date, the standard lead time will be 3 weeks.

Model 3742 Available Versions: ANY number of gauge lengths may be ordered with one measuring range that has matching units. The measuring range cannot exceed the gauge length. For gauge lengths not listed above, see models 3442, 3542, 3542L, and Epsilon ONE.

Example: 3742-3-ST, 3742GL-025M-3, 3742GL-050M-3, and 3742GL-080M-3: 25, 50, and 80 mm gauge lengths, +25 mm / -5 mm measuring range, standard temperature range (-40 °C to 100 °C)