Best Regards,
I'm working on a Wheatstone bridge using a DC source of 18 volts (two 9 V batteries in series), three resistance of 50 MΩ (actually each 50 MΩ resistance is two 25 MΩ resistors in series) and a variable resistance from 1MΩ to 50MΩ. My problem comes at the moment when I measure the voltage in the output of the bridge. It should measure 0V when no change is in the sensor that I'm using and around 9V when it is at its peak value of response. The measurements readings are around 2 V, no matter the input applied to the sensor. Later I took out the sensor and the left part of the bridge (leaving only the DC Source and four resistors of 25 MΩ each), to start troubleshooting my circuit. What I encounter was that between my ground and the last resistor, there was 18 V, but the voltage between any of the four resistors alone was around 2 V. The Ohm's law was being violated, as the voltage divider principle was failing. What I thought at that moment was that my DC Source wasn't giving me the amount of current that I need for, but I calculated and what I need are 0.54 µA. Then I tested with my laptop's DC power supply, that has a 12 V output with a maximum of 2 A, but I got the same results. The voltage divider principle was failing. Between all the resistors there were 12V, but on each one alone, there were only around 1 V. What is happening ? Does anyone knows what is the cause of this phenomenon? Can anyone suggest me what to do? Thanks for reading this thread, your suggestions would be very appreciated!.
Juan.
I'm working on a Wheatstone bridge using a DC source of 18 volts (two 9 V batteries in series), three resistance of 50 MΩ (actually each 50 MΩ resistance is two 25 MΩ resistors in series) and a variable resistance from 1MΩ to 50MΩ. My problem comes at the moment when I measure the voltage in the output of the bridge. It should measure 0V when no change is in the sensor that I'm using and around 9V when it is at its peak value of response. The measurements readings are around 2 V, no matter the input applied to the sensor. Later I took out the sensor and the left part of the bridge (leaving only the DC Source and four resistors of 25 MΩ each), to start troubleshooting my circuit. What I encounter was that between my ground and the last resistor, there was 18 V, but the voltage between any of the four resistors alone was around 2 V. The Ohm's law was being violated, as the voltage divider principle was failing. What I thought at that moment was that my DC Source wasn't giving me the amount of current that I need for, but I calculated and what I need are 0.54 µA. Then I tested with my laptop's DC power supply, that has a 12 V output with a maximum of 2 A, but I got the same results. The voltage divider principle was failing. Between all the resistors there were 12V, but on each one alone, there were only around 1 V. What is happening ? Does anyone knows what is the cause of this phenomenon? Can anyone suggest me what to do? Thanks for reading this thread, your suggestions would be very appreciated!.
Juan.
