M
Mark
- Jan 1, 1970
- 0
I'm designing a circuit to read the output from several pressure
transducers, buffer the signal and then digitize it.
The pressure transducer provides a 0-10V signal and the output is stated
as isolated. Contacting the Manufacturer (Taber) they state that they
use a small DC-DC converter within the unit to convert 28V to a lower
voltage to power the electronics inside the unit. Thus, the output is
floating and the low side of the output is not connected to the 28V RTN.
I want to read the signal differentially so I'm using an instrumentation
amplifier. Since the sensor is "floating" I placed a resistor from each
input (+ & -) on the amplifier to the local circuit ground to account
for the input bias currents. The resistors to ground in front of the
in-amp will set the common-mode of the sensor when the mux switch is
closed. So this should work OK for the selected channel through the mux.
But then I realized the other channels feeding the mux, that are not
selected, are still floating and do not have any reference to the mux's
ground.
Is this design acceptable, or should I reference the sensors output to
my local circuit ground on the input side of the mux also?
Thanks,
Mark
transducers, buffer the signal and then digitize it.
The pressure transducer provides a 0-10V signal and the output is stated
as isolated. Contacting the Manufacturer (Taber) they state that they
use a small DC-DC converter within the unit to convert 28V to a lower
voltage to power the electronics inside the unit. Thus, the output is
floating and the low side of the output is not connected to the 28V RTN.
I want to read the signal differentially so I'm using an instrumentation
amplifier. Since the sensor is "floating" I placed a resistor from each
input (+ & -) on the amplifier to the local circuit ground to account
for the input bias currents. The resistors to ground in front of the
in-amp will set the common-mode of the sensor when the mux switch is
closed. So this should work OK for the selected channel through the mux.
But then I realized the other channels feeding the mux, that are not
selected, are still floating and do not have any reference to the mux's
ground.
Is this design acceptable, or should I reference the sensors output to
my local circuit ground on the input side of the mux also?
Thanks,
Mark