# Circuit design for short-circuting outputs when needed

I am working with two sensors with 4 pin as output.
My question is simple: I want to make circuit that allows me to short circuit the output of either one of the sensors individually when needed.

I am considering using quad 1:2 demux (AGD774a) and shorting either the pins on channel B together while measuring with channel A and vice versa.
So when I want the channel for normal measurement I will use channel A and when I want output of sensor shorted I change the channel of the switch.

So, my main question is whether using a demux to solve the requirement is a wise choice or there is some other way it can be achieved.

Notes:

• The sensor is an ultrasonic transducer which produces only millivolt level outputs.

In use the sensor is placed in a heating chamber to increase its temperature.
When the temperature of the transducer is varied, it produces spurious temperature-change related voltages.
After heating we need to short the output pins to release all the residual voltage.
The charge itself is small.

May be I can do a worst case calculations and attach a resistance as well with it.

• The voltage drop is small - in the mV range.
I do not think that an electromechanical relay is required.

• The sensor will not be connected to Micro-Controller.
Shorting is needed to discharge the piezo in the sensor which occurs when the temperature is changed.

• Details of the sensor are really needed. Jul 16, 2014 at 12:19
• And explain what you want to achieve shorting outputs. Maybe you want to average? Or do you just want to connect your (uC?) input to a selected sensor? Jul 16, 2014 at 12:22
• Specifically, how much current can the sensor drive through the short, and how much voltage drop can you tolerate? You might need to use an electromechanical relay. Jul 16, 2014 at 12:35
• Actually the sensor(ultrasonic) I am using is not producing any voltage that is the shorting of signal is only required because if we put it in a temprature chamber to increase the temp we need to short the output pins to release all the residue charge. The charge it self is small. May be I can do a worst case calculations and attach a resistance as well with it . But my main question is using a demux to solve a problem like I explained before a wise choice or there is someother way it can be acheived. thanks Jul 16, 2014 at 12:36
• the voltage drop is small of mV range. No need of electromechanical relays for sure. Jul 16, 2014 at 12:39