I have a load that has varying resistance with external pressure. In order to measure the change, I am trying to measure the voltage on the load, when constant current is applied. And the circuit in the attachment is known to supply constant current using a transistor and a zener diode. But I have no idea what resistor/ transistor/ diode I need. I do not know if the circuit will burn them out.
The current on the load has to be approximately 6 mA, I think. And the supply voltage will be 5V. If needed, the transistor and zener diode I purchased are KTC3198, and 1N5231B-5.1V, respectively. The Vz (breakdown voltage of zener diode) will be 3.3V. Please comment, if any further information needed

 

and the DC CURRENT GAIN of the transistor will be 70

 

Why did you start a new thread?

I'd operate the zener at Izt, that's the current where Vz is valid. Data from OnSemi datasheet:

For the zener you're now going to use, that would be 20mA.



\( \small R = \frac{V}{I} = \frac{10V-3.3V}{20mA}=335\Omega \)

The closest 5% value is 330 ohms.

If your supply voltage is stable, you could use a lower current.

 

The zener diode has been changed. 1N5226B would be the one I will use. And the voltage across the diode will be 3.3V.

 

Please don't do double post, this thread will be locked, the original posted is here.