Part Number: DAC1282
Hi, I am trying to use DAC1282 and ADS1282 to test the detector’s leakage, which has been written in the datasheet for seismic applications. However, I am still not sure about the official suggested circuit for the detector leakage test. Can I use the following circuit? If so, what should I do?
Christopher Hall | Δ-Σ Data Converter ApplicationsTI.com | TI Precision Designs | Selection Guide | Technical Documents | Tools & Software | Design Notes | E2E Site Map
In reply to Christopher Hall:
Firstly I was trying to measure the leakage impedance.
In reply to user4687076:
I think this could be accomplished with this circuit:
The basic concept is that by comparing the voltage reading(s) on either side of the resistors you know the voltage drop across them. Form there you can calculate the current, knowing the values of the resistors.
Thank you for your reply. However, what you proposed is the circuit to know the actual built-in resistance of the geophone, while I was asking to test the LEAKAGE resistance.
I'm afraid I need a bit more more information... Is the geophone earth-ground referenced? What other input circuitry (filter, protection, etc.) or components are you using? What is the main leakage current path that you're trying to measure?
Likely, you could still use something similar to the above circuit concept; however, you will certainly need to tweak it to your specific application.
Sorry for the delay. I think you could adapt the above circuit to do one of the following measurements:
Perhaps you could use the second ADC channel to measure the I3 current directly (across the resistor). If you wanted to measure I1 and I2, then you would probably need to use some external switches to measure make the connections across each of the input series resistors.
Note that whatever source you use to provide these currents will need to be connected to earth ground.
Could you please provide a precise equation of the group delay of the digital filter chain? The 31/fdata one on the datasheet is too rough for us.
I think the group delay is much more accurate than 1/fdata. The digital filters are driven by a clock much faster than fdata. The actual group delay is related to clock frequency rather than fdata. Same applies to tdr (time to data ready), which has a very accurate equation. Actually we measured the group delay at 1k SPS. The result is 31.269 us to the accuracy of less than 1us. But we still need the theoretical equation to confirm our measurement.
We did calculate the group delay using coefficients in the appendix. But this group delay is a purely theoretical. A more accurate equation should consider the actual digital circuit, such as the timing of registers.
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