Hi all,
I'm developing a circuit that takes ultrasonic input and transmit it to the receiver. I'm using a video transmitter to cover ultrasonic range (my target range is 40Khz) The receiver is connected to an oscilloscope for reading through BNC cable.
When I read the output of the receiver, the oscilloscope input setting was AC coupling with 50oHm impedance. When I choose this setting, the osccliscope display the message saying :
The combination of AC and 50 ohm produces a very high lower frequency limit.
The table shows the maximum lower frequency cutoff for all coupling/impedance combinations.
1Mohm 50ohm
AC 10 hz 200khz
DC 0 hz 0hz
- Message end -
In this setting, the output of the receiver is similar to input signal of transmitter with gain less than 1. It is shown figure 1. below.
figure 1.
However when I connect this to DAQ (AC coupling, and high input impedance), then the output looks like figure 2. below. The output has lots of gain and couple with the DC voltage(I think).. The output data through DAQ is same as oscilloscope reading with AC coupling with 1M ohm impedance setting ( or DC coupling with 50 ohm or DC coupling with 1M ohm setting. They are same)
figure 2.
I'd like to design an extra circuit that would be placed between output of the receiver and input of the DAQ, and works like AC and 50ohm setting..
SO far, I tried changing input impedance by placing resister in parallel when the oscilloscope setting is 1M ohm. However, it doesnt work. It only changes gain of the output of the receiver...
Please let me know if you have any idea to design an additional function between DAQ and the receiver (I guess filter function)
Best Regard
Justin
I'm developing a circuit that takes ultrasonic input and transmit it to the receiver. I'm using a video transmitter to cover ultrasonic range (my target range is 40Khz) The receiver is connected to an oscilloscope for reading through BNC cable.
When I read the output of the receiver, the oscilloscope input setting was AC coupling with 50oHm impedance. When I choose this setting, the osccliscope display the message saying :
The combination of AC and 50 ohm produces a very high lower frequency limit.
The table shows the maximum lower frequency cutoff for all coupling/impedance combinations.
1Mohm 50ohm
AC 10 hz 200khz
DC 0 hz 0hz
- Message end -
In this setting, the output of the receiver is similar to input signal of transmitter with gain less than 1. It is shown figure 1. below.
figure 1.
However when I connect this to DAQ (AC coupling, and high input impedance), then the output looks like figure 2. below. The output has lots of gain and couple with the DC voltage(I think).. The output data through DAQ is same as oscilloscope reading with AC coupling with 1M ohm impedance setting ( or DC coupling with 50 ohm or DC coupling with 1M ohm setting. They are same)
figure 2.
I'd like to design an extra circuit that would be placed between output of the receiver and input of the DAQ, and works like AC and 50ohm setting..
SO far, I tried changing input impedance by placing resister in parallel when the oscilloscope setting is 1M ohm. However, it doesnt work. It only changes gain of the output of the receiver...
Please let me know if you have any idea to design an additional function between DAQ and the receiver (I guess filter function)
Best Regard
Justin
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