Hi folks,
I have a query which i'm sure is a stupid one but I am having trouble measuring the signal seen at my receiver ultrasonic transducer. I few days ago I tested my transmitter circuit by monitoring the signal seen at the receiver and all was good. I had a nice clean stable signal while the scope (i'm using a picoscope) and ground reference clip was connected between the sensor pins.
Well today I had connected up my amplifier and charge pump, ready to move into the signal conditioning section. I connected the receiver to the input of the amplifier and turned it on. I had one probe connected to the receiver legs as before and a second probe connected to the output of my amplifier. The scope was set up to trigger on the receiver signal but the signal was so erratic it was going out of range and constantly triggering the scope. the "0V" signal was basically all over the place.
I first thought I must have done something with the amplifer circuit so I disconnected the receiver from the breadboard however the "0V" was still floating all over the place. I removed the wires from the sensor and this improved the stability but it was still floating around when the receiver was close to the transmitter. As I moved it further away the signal stablised so it looked like it did when I tested it a few days ago.
I played around with it and i found if anything metal touched the pins the signal became erratic, even the end of an insulated screwdriver.
The thing is, this did not happen at all when I tested it previously. Even when the sensors were practically touching the "0V" was completely steady and I got good clean waveforms as I was expecting.
Can anyone suggest what I might be doing wrong? I know the signal is not references to anything so it does technically float but if you are measuring between the pins I would expect the signal to be stable. If I put wires back onto the sensor and re-connect it to my amplifier I have no way to properly trouble shoot if the circuit doesn't work so I'm hoping what is happening has a "fix" that I can implement before moving on.
Thanks in advance.
I have a query which i'm sure is a stupid one but I am having trouble measuring the signal seen at my receiver ultrasonic transducer. I few days ago I tested my transmitter circuit by monitoring the signal seen at the receiver and all was good. I had a nice clean stable signal while the scope (i'm using a picoscope) and ground reference clip was connected between the sensor pins.
Well today I had connected up my amplifier and charge pump, ready to move into the signal conditioning section. I connected the receiver to the input of the amplifier and turned it on. I had one probe connected to the receiver legs as before and a second probe connected to the output of my amplifier. The scope was set up to trigger on the receiver signal but the signal was so erratic it was going out of range and constantly triggering the scope. the "0V" signal was basically all over the place.
I first thought I must have done something with the amplifer circuit so I disconnected the receiver from the breadboard however the "0V" was still floating all over the place. I removed the wires from the sensor and this improved the stability but it was still floating around when the receiver was close to the transmitter. As I moved it further away the signal stablised so it looked like it did when I tested it a few days ago.
I played around with it and i found if anything metal touched the pins the signal became erratic, even the end of an insulated screwdriver.
The thing is, this did not happen at all when I tested it previously. Even when the sensors were practically touching the "0V" was completely steady and I got good clean waveforms as I was expecting.
Can anyone suggest what I might be doing wrong? I know the signal is not references to anything so it does technically float but if you are measuring between the pins I would expect the signal to be stable. If I put wires back onto the sensor and re-connect it to my amplifier I have no way to properly trouble shoot if the circuit doesn't work so I'm hoping what is happening has a "fix" that I can implement before moving on.
Thanks in advance.