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3136_0_Datasheet - May 13, 2011

Datasheet

3136 - Button Load Cell (0-50kg) - CZL204E

What do you have to know?

A load cell is a force sensing module - a carefully designed metal structure, with small elements called strain gauges

mounted in precise locations on the structure. Load cells are designed to measure a specic force, and ignore other

forces being applied. The electrical signal output by the load cell is very small and requires specialized amplication.

Fortunately, the 1046 PhidgetBridge will perform all the amplication and measurement of the electrical

output.

How does it work - For curious people

Strain-gauge load cells convert the load acting on them into electrical signals. The measuring is done with very small

resistor patterns called strain gauges - effectively small, exible circuit boards. The gauges are bonded onto a beam

or structural member that deforms when weight is applied, in turn deforming the strain-gauge. As the strain gauge

is deformed, it’s electrical resistance changes in proportion to the load.

The changes to the circuit caused by force is much smaller than the changes caused by variation in temperature.

Higher quality load cells cancel out the effects of temperature using two techniques. By matching the expansion

rate of the strain gauge to the expansion rate of the metal it’s mounted on, undue strain on the gauges can be

avoided as the load cell warms up and cools down. The most important method of temperature compensation

involves using multiple strain gauges, which all respond to the change in temperature with the same change

in resistance. Some load cell designs use gauges which are never subjected to any force, but only serve to

counterbalance the temperature effects on the gauges that measuring force. Most designs use 4 strain gauges,

some in compression, some under tension, which maximizes the sensitivity of the load cell, and automatically

cancels the effect of temperature.

Installation

This Button Load Cell is used in applications that require a thin form factor. The bottom of the load cell is bolted,

and force applied to the button on the top. By loading only the button, which is slightly rounded, the load cell is less

sensitive to errors resulting from the load not pushing down exactly straight on the load cell.

Contents

1 What do you have to know?

1 How does it work - For curious people

1 Installation

2 Calibration

2 Product Specifications

3 Glossary

Summary of content (4 pages)

PAGE 1
Datasheet 3136 - Button Load Cell (0-50kg) - CZL204E Contents 1 1 1 2 2 3 What do you have to know? How does it work - For curious people Installation Calibration Product Specifications Glossary What do you have to know? A load cell is a force sensing module - a carefully designed metal structure, with small elements called strain gauges mounted in precise locations on the structure. Load cells are designed to measure a specific force, and ignore other forces being applied.
PAGE 2
Calibration A simple formula is usually used to convert the measured mv/V output from the load cell to the measured force: Measured Force = A * Measured mV/V + B (offset) It’s important to decide what unit your measured force is - grams, kilograms, pounds, etc. The specification is in kilgorams, but you can generate the formula for whatever unit of measure you need. The Certificate that is included with your load cell will specify an exact rated output. As an example, assume the rated output is 1.
PAGE 3
Glossary Capacity The maximum load the load cell is designed to measure within its specifications. Creep The change in sensor output occurring over 30 minutes, while under load at or near capacity and with all environmental conditions and other variables remaining constant. FULL SCALE or FS Used to qualify error - FULL SCALE is the change in output when the sensor is fully loaded. If a particular error (for example, Non-Linearity) is expressed as 0.1% F.S., and the output is 1.
PAGE 4
Safe Overload The maximum axial load which can be applied without producing a permanent shift in performance characteristics beyond those specified. Compensated Temperature The range of temperature over which the load cell is compensated to maintain output and zero balance within specified limits. Temperature Effect on Span Span is also called rated output. This value is the change in output due to a change in ambient temperature. It is measured over 10 degree C temperature interval.