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Glossary of specification terminology

Accuracy

The degree to which something is true or exact.

As an example, consider the characteristics of the TSD202A temperature transducer. With this transducer, there is an intrinsic accuracy of 0.2 °C between TSD202A units. This means for a specifically identified (true or exact) temperature, TSD202A units should read that temperature but may be over or under by as much as 0.2 °C.

Creep

Change in output for a given load for a long time period, typically measured in hours or days.

For instance, the TSD121C has a creep value rated at < 0.05% after thirty minutes.  This means that if a 50 kg mass is hung from the device, after 30 minutes the device should report a value between 49.975 and 50 kg.

Hysteresis

Non- linear phenomenon which means the positive going slope is offset from the negative going slope.

Ideally, any time that a sensor is exposed to the same quantity, it should produce the same response.  In reality, the response of a sensor may depend on the history of the quantities to which it has been exposed.  The TSD121C dynamometer is subject to hysteresis.  When squeezed with a given force, the transducer may not always respond the same way.  This is mostly evident when the device is exposed to a compressive force and is then quickly placed in tension.  The device will continuously report changes to the forces applied to it, but its accuracy will vary across a compression/tension cycle.  By design, hysteresis should be a small quantity.  The specification is less than ±0.02% of rated output, so for instance, if the force it is exposed to at a particular point in time is 9.8 kg (engineering definition of “kg” — meaning the force experienced by an object of 1 kg mass in a 1 g gravitational field), the force it reports should be between 9.798 and 9.802 kg.

Linearity

The degree to which a relationship between cause and effect is exactly proportional.

As an example, consider the characteristics of the TSD125C force transducer. With this transducer there is defined relationship between output voltage and beam deflection due to applied force. A perfectly linear force transducer would increase its output signal in direct proportion to the beam deflection. The TSD125C Full Scale Range (FSR) is 50 grams of force, and at this point the transducer output is maximized (Vmax). If only 5 grams of force were applied, a perfectly linear force transducer would output exactly 10% of Vmax. The non-linearity of the TSD125C is less than 0.025% of FSR. This means that the TSD125C may report a value which could be as much as 0.025% different from an exactly proportional value. For a beam deflection that would ideally produce a 1 mV signal, the TSD125C should report a signal between 0.99975 and 1.00025 mV.

Non-repeatability

The inability to perform the identical measurement twice.

If the output signal of a device with a nonrepeatability specification of < ±0.02% is 3 mV on one trial and the device is later exposed to the same physical quantity, the output signal should be between 2.9994 and 3.0006 mV.

Normalized Excitation

As an example, if the nominal output spec is 13.2 µV/kg, the normalized excitation is 13.2 µV/kg for 1 V excitation. At 10 V excitation (highest setting for the DA100C General Purpose Transducer Amplifier), output is 132 µV/kg.

Resolution

The fineness of detail that can be determined in a signal.

As an example, consider the resolution of the MP150 A/D converter. This converter has 16 bits of resolution. Two to the 16th power is 65,536. Accordingly, the MP150 A/D converter is capable of resolving 65,536 levels of signal amplitude between -10 V and +10 V. Consequently, the resolution of the MP150 A/D converter is 20 V divided by 65536 or approximately 300 uV per bit (level).

Touchproof

1.5 mm male (pin) and female (socket) connectors.

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