Frequency response.

<p>Frequency attenuation of the signals measured with the reference-sensor (dark grey trace) and the load-cell (black trace), in combination with the attenuation predicted by the calculated model of the load-cell (light grey trace). The model fits the measured load-cell data well at lower frequencies. For frequencies higher than 10 Hz a further decrease is observed in the measured data, revealing a maximal attenuation of -4.2 dB at a frequency of 200 Hz.</p

Reproducibility.

<p>An 1 kg (9.81 N) weight was used on 5 different days to test the practical reproducibility of the load-cell’s. On each day the load-cell measured 5 consecutive loading/unloading cycles. The active force (V_diff = V_max−V_offset) was determined for each loading. Values expressed as voltage-difference () and standard deviation (SD).</p

Working principle of the load-cell.

<p>A: Schematic representation of the clamping mechanism of the load cell. The illustration shows the dimensions of the load-cell as well as the position and orientation of the strain-gauges (SG) of the front side. The SGs on the back-side are positioned and orientated analogously. The circuit in the lower left corner shows the connection of the SG´s as temperature compensated half-bridge B: Manufactured load-cell in comparison to a 5 Euro-cent coin without clamping screws.</p

Hysteresis.

<p>Hysteresis was obtained by superimposing four consecutive responses, to a triangular force-pattern, measured with the load-cell. The hysteresis shows its highest width at 9.84 N which amounted to 30 μV / V.</p

Tendon shrinkage.

<p>Measurement of the relative shortening during drying of the tibialis anterior tendon of a rat.</p

Calibration curve.

<p>Change in output-voltage (V_diff) normalized to the bridge voltage (0.562 V) of the load-cell in relation to changes of force (F_diff), measured with rectangular force pulses of different amplitudes. Crosses depict the results of the individual measurements for each force-level (amplitude). The individual measurements appear as single cross in the diagram due to the low variation. The solid grey line shows a linear regression performed on this data.</p

Calibration curve measurements.

<p>Measurement results presented as mean voltage-difference () and standard deviation (SD). The spreading of the data is reported as relative difference to of the minimal and the maximal individual measurement of V_diff for each force-level. Further data of the overall linear regression (V_{diff_linear}) and the corresponding absolute linearity error (– V_{diff_linear}) are illustrating the load-cell´s linearity.</p

Step response.

<p>A) Illustration of the normalized signals measured with the reference sensor (dark grey trace) and the load-cell (light grey trace). The black trace represents a fitting (R² = 0.977) to the normalized load-cell signal, considering the normalized reference-signal as input. The model of the load-cell is represented schematically as block-diagram of an additive combination of a P and two PT1 elements with the overall behavior of a PD2T2 element. B) The inverse transfer function of the PD2T2 model was used to correct the force response of a single twitch and a short burst (stimulation frequency 60 Hz). The exemplary data reveals an underestimation of the measured peak-forces by 14.3% for single twitches and 6.8% for short bursts.</p

Measurement setup.

<p>A Bose linear motor applied preprogrammed patterns of force to the newly developed load-cell. The force measured with the reference sensor was used to correlate the output voltage of the load-cell with the load applied. The load-cell was tested using a dried tibialis anterior tendon of a rat which connected the device to the measurement set up.</p

Ratings of the three applied substances CO₂, menthol and cinnamaldehyde.

<p>^a Bonferroni corrected</p><p>^b High values indicate pleasant/ familiar stimuli</p><p>^c High values indicate painful stimuli</p><p>^d Percentage of subjects who were able to label the substance correctly</p><p>Ratings of the three applied substances CO₂, menthol and cinnamaldehyde.</p