POT4

Also see : POT4a and POT4b

Power Supply

+12V, GND, -12V required.
Absolute maximum supply voltage is +-15V
Supply current (DC input, no load) < 50mA (35mA typical)
Due to the outputs driving 1uF capacitive loads, there is an additional AC supply current
Position output load current : I = (1uF) * 2*pi*f*Vo*sqrt(2)/2 or 4.4e-6 * f * Vo - thus a 100Hz 10V sine wave adds 4.4mA to the position output
Differential output load current : Vout = ~1e-6 * dVi/dT so I = (1e-6)*(2*pi*Vo)^2 * 1e-3 * sqrt(2)/2 or 2.8e-8 * (f*Vo)^2
a 50Hz, 10 Hz input has 2.2mA load from the position output, and 7mA on the velocity output

a 100Hz, 10 Hz input has 4.4mA load from the position output, and 28mA on the velocity output

POT4

top side

bottom side

(DL1, DL2) : A pair of single LEDs indicate the present of power. These LEDs are aligned with the power input to the boards.
- RED : configured for potentiometer inputs (#1-2)
- GREEN : configured with bridge inputs (#3-8)
DK1 : The intensity of this dual RED/GREEN LED indicates the voltage of the "position signal".

JF1 : 3 way jumper used to select source that drives that "Position" output. The signal source may be one of the following:
- Instrumentation amplifier output
- 2nd order low pass filter output
- 4th order low pass filter output

JC1 : selects the "Shield" header signal source and is specified at assembly time. Signal sources include "GND", "COM", or "REF-".

POT4 can be built for either potentiometer input or bridge input. There are also several optional circuit modules.

boards #1, #2 : fully built with lowpass filters, differentiation and configured for potentiometer input. These boards use the LT1167 with gain G=1+49.4K/RA1.

boards #3, #4 : minimally built for strain gauge bridge input. These boards use the INA122 with gain G=5+200K/RA1. Opamp LM324, 100K trim pot

boards #5 - #8: built for strain gauge bridge input and are minimally built with 2nd order LP filter. These boards use the INA128 with gain G=1+50K/RA1. Opamp LM324, "503" trim pot