Electronics > Projects, Designs, and Technical Stuff
Op Amp transient analysis
Vettett15:
Got some interesting data today on the bench. I was able to get my hands on a usb oscilloscope so i hooked up both the OEM sensor (yellow trace) and my sensor with the TLV4111 op amp (blue trace).
i manually opened the sensor's flap (rise in voltage), held it there and then let it go (spring loaded). Concentrating on the voltage drop because the springs between the units should be relative consistent.
Note that the noise on the yellow trace is due to the oem sensor's carbon trace wearing out.
I thought the most interesting thing was that the stair steps on the TLV4111 sensor looks like it takes ~12ms to change voltage, seems slow to me, no?
Note these were done with no load on the output.
T3sl4co1l:
Looks like zoomed DSO with sinx/x interpolation turned off. In other words, instrument error, RTFM and all that; repeat the measurement at the zoomed-in setting and see if it's still smooth.
Tim
Vettett15:
Tim, if that was the case then why don't I see the stair step on on the oem measurement? Took them both at the same time
T3sl4co1l:
Oh, they are on the same scales, aren't they?
Beats me, but something's doing a sample and zero-order-hold operation.
Tim
Vettett15:
Well I put the new sensor on the car and immediately realized my first issue.... Looks like the ecu can only supply wmA while maintaining the voltage and my design pulls 29ma... The voltage is getting pulled down to 3.5v which causes it to not function properly.
Somehow I need to figure out how to drop current consumption. The a1335 magnet sensor chip pulls 15 mA alone.
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