Sensitivity expressed in mV per mm equals the full-scale output in mV divided by the calibrated mechanical range in mm, a conversion process useful for position transducers, extensometers, and other strain-gauge based sensors where the spec sheet lists mV/V rather than mV per displacement [S3][S5].
For a sensor rated 1 mV/V on a 100 mm range powered by 10 VDC, the full-scale output is 1 mV/V × 10 V = 10 mV, which divided by 100 mm gives 0.1 mV/mm; this is the figure that an indicator or DAQ card should expect per millimetre of travel [S3].
The core formula and a worked example
The general calculation is sensitivity (mV/mm) = (mV/V rating × excitation voltage) ÷ measurement range in mm, as illustrated in strain-gauge pressure and position references where a 1 mV/V/bar sensor on 10 VDC across 10 bar delivers 100 mV full scale, or 10 mV per bar [S3].
Step-by-step: with 2 mV/V sensitivity, 10 VDC excitation, and a 50 mm calibrated range, full-scale output is 2 mV/V × 10 V = 20 mV, and 20 mV ÷ 50 mm = 0.4 mV/mm; halving the excitation to 5 VDC drops the figure to 0.2 mV/mm, confirming why low-voltage excitation compounds noise problems in long cable runs [S1][S3].
The same ratiometric logic drives load-cell maths: a 2 mV/V cell with 10 VDC excitation and a 1000 kg rated capacity delivers 20 mV at full load, or 0.02 mV per kilogram, so converting that to mV per mm requires knowing the millimetres of deflection corresponding to the applied kilogram load [S2].
From load-cell mV/V to mV per mm of deflection
Load cells and LVDT-style position sensors share the same Wheatstone-bridge physics, but the mV/V rating only gives output per unit load; to get mV per mm, multiply by the cell's mechanical stiffness expressed in mm of travel per unit load [S1][S5].
A 1000 kg load cell with 0.05 mm deflection at full scale and 2 mV/V sensitivity on 10 VDC produces 20 mV full scale, so the equivalent position sensitivity is 20 mV ÷ 0.05 mm = 400 mV/mm, a useful conversion when the same body is being used as both a load and displacement sensor [S2][S5].
National Instruments notes that pressure transducers are sometimes rated with combined units such as 10 mV/V/mmHg, meaning the per-volt output is normalised to the per-mmHg pressure step, which is the same form as mV per mm when the input variable is linearised [S5].
Where the unit comes from in sensor datasheets
Span sensitivity in strain-gauge sensors is defined as the output per volt of excitation independent of range or supply, a ratiometric definition that allows engineers to compare devices on a common scale before scaling back to engineering units [S3].
Blood-pressure transducers cited in standard sensor textbooks are typically rated 5 µV/V/mmHg, equivalent to roughly 1 mV per mmHg at 200 mmHg full scale with 10 VDC, an example of the same mV/V principle applied to a non-millimetre input variable [S4][S5].
Position transducer calibration calculators record the same parameter as a single number in mV per unit travel; a sample 10 VDC, 4 V excitation, 10-unit range with measured points stepping from 2.4 to 3959 yields a 98.915 mV-per-unit sensitivity, matching the ratio of full-scale output to range [S6].
How mV per mm maps to instrumentation inputs
Once the mV/mm figure is known, the indicator or DAQ range must be selected so that the smallest resolvable step exceeds the analogue-front-end noise floor, typically a few microvolts for 24-bit systems and tens of microvolts for 16-bit industrial PLCs [S3][S5].
For a 0.1 mV/mm position sensor, a 24-bit DAQ at ±10 V range resolves about 1.2 µV per count, giving roughly 0.012 mm resolution; the same sensor on a 16-bit PLC at the same range resolves about 305 µV per count, or 3 mm, so the mV/mm figure directly drives instrumentation choice [S1][S5].
For a closer look at how micro-signal sensors integrate with plant controllers, see this comparison of board-level versus housed cameras for embedded integration, which follows the same signal-chain trade-off between native sensor output and downstream electronics headroom [S3].
Typical values and selection trade-offs
Most industrial load cells fall in the 1 to 3 mV/V range, with 2 mV/V as the de-facto standard; converting that to mV per mm depends entirely on the spring element's stiffness, so a 1000 kg cell rated 2 mV/V may produce anywhere from tens to hundreds of mV per millimetre of body deflection [S1][S2].
Higher mV/V ratings, 3 to 4 mV/V and above, are reserved for precision test benches and laboratory force measurement where resolution of very small increments matters more than overload margin, while 1 to 2 mV/V cells are chosen for truck scales and silos where surviving impact and cycling is the priority [S1][S2].
Engineers who must mount a sensor in a tight axial envelope should review this reference on button load cells for tight axial spaces, since the mV per mm figure in those compact geometries often sits at the high end of the family to compensate for shorter spring travel [S2].
Error sources: linearity, drift, and excitation stability
Sensitivity drift is the change in the slope of the input-output line over time or with temperature, distinct from zero drift which shifts the intercept; the two are usually specified separately in datasheets as %FS/°C and %FSO/°C respectively [S4].
A worked non-linearity example uses a 10 mV/psi pressure transducer: a measured output that departs from the best-fit straight line by 0.5 mV at mid-scale represents 5% of full-scale non-linearity, and the same percentage logic applies to mV/mm when checking position-sensor linearity [S4][S7].
Excitation voltage tolerance directly scales the mV/mm number: a 10 VDC supply regulated to ±0.05% holds the mV/mm figure to within the same percentage, while an un-regulated supply swinging ±5% injects the same swing into the sensitivity, which is why ratiometric ADC references are preferred [S1][S8].
Conversion to engineering units and span calibration
The two-point span calibration workflow uses the same mV/mm math: apply a known low-end displacement, record mV output, apply a known high-end displacement, record mV output, then solve slope = (mV_high − mV_low) / (mm_high − mm_low), and offset = mV_low − slope × mm_low [S8].
For a position sensor tested from 0 to 100 mm with output stepping from 2.4 mV to 3959 mV at 10 VDC, slope is (3959 − 2.4) ÷ (100 − 0) = 39.566 mV/mm, with offset 2.4 mV; any mid-range linearity error is read against the same best-fit line that defines the published mV/mm figure [S6][S7].
For 4-20 mA current-loop conversions of the same sensor, the mV/mm figure is converted via the loop resistor, typically 250 Ω, giving 1 mV/mm = 0.25 mA/mm at the receiver; the same ratiometric principle lets the indicator treat excitation drift as a common-mode signal that cancels out [S3][S8].
Track the following two signals in 2026 datasheet revisions: (1) a move toward 3 mV/V as the new industrial standard for general-purpose cells as precision-strain gauge costs fall, and (2) tighter span-sensitivity tolerances of ±0.05% rather than the historical ±0.1% on premium cells, both verifiable against the next revision of manufacturer calibration certificates [S1][S2].
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