thanks sir randy for another great and excellent presentation you have for sensor...hoping another class lesson for sensor part 3 or controllers that would be another great sir!
thanks to digikey and design news for another continuing education. now, i am going to the last class seeion of day 5 of sensor class...
thanks to all colleagues and see you all in the next live class session this coming june 10...bye...
Good presentation, thank you. A lot of App Notes are available to help with interface issues such as cabling, board layout, PWB design, bypassing and such like. CMRR also helps a lot. Device vendors for both sensors and interface IC's have done good work in paving the way. Realize these are reference designs, mileage may vary ...
Do these sensors also have 4 to 20 ma output capability?
None of the sensors I discussed today had the option of 4-20 mA output. From what I know, for a 4-20mA signal conditioner, you have choices from Analog Devices, TI, Melexis and probably a few more to get the 4-20 ma capability (and perhaps then you get a digital output as well.)
I've been able to recalibrate humidity sensors to within 2-3% accuracy using measured values, but its not just a simple offset. There are calibration devices out there as well but haven't tried any
The interface chips outlined in today's presentation use either I2C or SPI interfaces to the microcontroller. Other than speed differences and the number of pins required, what other considerations drive the chip vendors to select one interface over the other?
While there could be difference that would make one preferred over the other, I think the real answer is suppliers want to satisfy designers with an approach they are most familiar with. If you offer both, you cover a lot of bases.
Thanks, very interesting presentation. Can you mention where these sensors are available from?
Since today's session strictly focused on the sensor singal conditioning no specifc sensors were discussed. Outside of contacting the IC manufacturers, your favorite distributor might be a good palce to start for the ICs.
If you want an idea of sensor manufacturers for various sensing technologies, TI's WEBENCH suggest manufacturers and products once you have selected, temperature, pressure, etc.
I'm curious about the temp. pressure sensor with the MAC90100. Is the sensor also campable of simultaniously sensing both variables?
The pressure sensor is external the temperature sensing is internal and the device must be switched between the two. For the temperature to apply to more than the IC, it must be in close proximity to the sensor.
If you want to experiment with gas sensors, take a look at Parallax, Inc - They have a number of different sensors on development boards or as bare sensors
If the signal conditioning electronics can't be co-located with the sensor itself can you say a few things about reducing noise on the input lines to the conditioning circuitry?
That where a high common mode rejection ratio value would come into play.
Great tips. I didn't know about the TI tool and AFEs. Those ICs should really make life easier. no more nerve wracking instrumentation amps. Thanks a lot Randy.
Randy: You have shown "signal conditioning" in the analog part of the game. How about "fixing things in post", i.e. in the MCU/DSP?
I should have mentioned that with the capability of MCUs and DSP and DSC these are frequently used and the only thing you need from the analog part is the amplification. The internal ADC and software can allow very precises sensor calibrations expecially if they are each tested to detemrmne the specific calibration variables.
If the signal conditioning electronics can't be co-located with the sensor itself can you say a few things about reducing noise on the input lines to the conditioning circuitry?
In using the MAS6502 for temp and pressure, are these measurement taken from a single bridge sensor? Does it mean the sensor is subject to both physical variables?
@jrjohns: My experience boils down to I2X being mre capable (multi-point bus, any node can be master. slave, or both, etc.) but is more expensive in both dies are and time to implement. Also should "register" an I2C to be real I2C.
The interface chips outlined in today's presentation use either I2C or SPI interfaces to the microcontroller. Other than speed differences and the number of pins required, what other considerations drive the chip vendors to select one interface over the other?
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