Q:
I am building a test machine to automate the calibration process for MLX90320 pressure sensor, using the EVB90320 and the PSF sw libraries.
3 questions about 90320:
1) The PC has 4 serial ports, one of them connected to the EVB90320.
At startup, I use a certain code to connect the EVB.
This procedure performs scanning of all serial ports, transmitting 3 bytes to poll for an EVB connected.
I want to specify the serial channel connected to the EVB, in order to avoid that all the devices connected to other serial ports receive the 3 polling bytes.
How can I do this ?
If I connect the EVB to USB how could I specify to scan only USB channels and not serial ports?
2) When the function "ProgramDevice" returns, could I immediately switch off the circuit if the eeprom programming is still in progress?
3) Is it possible to connect more than one EVB to the PC (to serial port or USB)? If yes how can I address each EVB using the PSF functions?
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A:
Apparently there is a problem with the PSF library, so that CheckSetup function always rescans available serial ports, even if the port is already specified.
Regarding usage of USB - that code is perfectly applicable, only the correct "virtual" seial port must be specified.
2) When the function "ProgramDevice" returns, could I immediately switch off the circuit or the eeprom programming is still in progress?
There is no problem to switch off the board as the function ProgramDevice has returned.
3) Is it possible to connect more than one EVB to the PC (to serialport or USB)? If yes how can I address each EVB using the PSF functions?
It is possible to connect more than one evb to the pc. You can check the PSF90320 documentation which is stored onto the cd.
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Q:
I have an evaluation board for the MLX90320, but I don't have any datasheet or documents. What do I need to do?
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A:
The MLX90320 datasheet is available on our website. You can do search via the search box on the top left corner of each page on our website.
The Evaluation Board is delivered with a CD containing the software as well as the documentation.
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Q:
I cannot get MLX90308 to Operate in Digital Current Mode. It works OK in Analog Current or in Digital Voltage but when I change from Analog Current to Digital Current I get no signal on CMO pin. When I look at Signal In Value everything appears OK. Also if I enable both Current and Voltage Mode (which is allowed in Digital Mode) again VMO pin responding but not CMO pin. I am using MLXconfig 1.e as software.
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A:
We have a dll available for both MLX90308 and MLX90314 which you can use to build up your own calibration algorithm. By using this you can significantly decrease the calibration time.
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Q:
Has anyone noticed a change in the high temperature performance of the new version D of the MLX90308/90314? I'm observing a non-linearity in the low range (0-10% of full scale), at temperatures 110C - 140C. I'm not seeing this with our older "CA" chips. The sensors we use aren't the source of it (I checked). If I'm the only one with this problem - maybe I should reevaluate my design. Do you have any thoughts on what pins might be sensitive to component selection (sensor ~1-2kohm, 0.1 to 4.7uF bypass capacitors, ESD protection, etc.)?
I am in absolute mode. The output load is a 0.1uf cap, 11V zener diode, and DVM in parallel, all to ground. I used the same application circuit for CA and DA, but now I've removed the 5k resistor recommended in your application circuit - this helped remove some high-temperature non-linearity.
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A:
If you keep a PD of about 10k and that you calibrate the output offset to a value higher than 150mV you should not have linearity problems at high temperatures.
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Q:
How can we perform the temperature compensation with the 90308?
We would like to calibrate our device to have a acceptable result over the full temperature range (-40 to 140).
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A:
The figure 3 (Temperature Linearity Correction) of the datasheet will help you to understand what your engineer wants to do. Let me assume that the temperature range of your application is -40degC till 140degC. Your engineer wants probably to use 75degC as T1 (see figure 3 of the datasheet) and find the optimal coarse and fine settings at this temperature than use 0degC to find the appropriate values of GNTC1 and OFCT1 and eventually go to 130degC to find GNTC2 and OFTC2. In this case you will have at the end 2 temperature gaps: the first will be for a temperature lower than 75degC and the second for a temperature higher than 75degC. In the software you have to fill in the following values: - Coarse Gain, Coarse offset, Fixed gain, Fixed offset found at 75degC - Temp Gap1 is the temperature code at 75degC -OFFTC1 and GNTC1 found at 0degC -OFFTC2 and GNTC2 found at 130degC -Temp Gap2 will be in this example equal to 1023.
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Q:
SW90308 allows the user to program integrated EEPROM of MLX90308D, but it seems unable to program MLX90308CA.
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A:
The SW90308 allows to program both the MLX90308DA and MLX90308CA. To solve communication problems with the CA you can do the following: - use a non standard baud rate for the communication. - copy the EEPROM contents of the address 32 to 34 (CLKTC parameter) stored on a chip that shows no communication problems to the chip giving troubles. - disable the turbo bit.
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Q:
Can the COMS pin be left unterminated or is a pull-up resistor required for stable operation?
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A:
You need to use a pull up of 5K.
This will guarantee that ther will no signals been picked up on the COMS line.
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Q:
I used the MLX90320 and have some troubles,please help me,thanks.
The MLX90320 can calibrate with 3 point of temperature,it contain low temperature,normal temperature and high temperature.
When I calibrated the points of normal temperature and low temperature,I have to find a
condition with high temperature to calibrate,but that place far away from the case of the low temperature.
So the EVB90320 will be lost the power supply.
When I arrive another place and Re-provide the power,the steps of the calibration be lost too.
But the data in the EEPROM was exist,just the steps were lost.(3 temperature point set off 9 steps,the step must be perform one by one)
My problem is that how to complete the calibration of the last temperature(last 3 steps) in the case of mentioned above.
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Q:
Sorry if this sounds like a dumb idea, but if I understand your setup correctly, you need to move the sensor (and calibration equipment) to another location within your building to complete your calibration. Is this correct?
Could you put your programmer and associated equipment on a rolling cart? If so, you could use a computer UPS (Uninterruptable Power Supply) to keep the equipment operational while you move the cart. UPS systems are fairly cheap and provide AC line filtering as a bonus.
Just plug everything in with the UPS in-line and start your calibration, then pull the AC plug and roll everything to the high temperature place, plug the AC cord back in, and you should be able to complete your calibration.
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A:
If you really have to switch off the power supply between
the second and third calibration temperature you can also
perform the calibration without the solver. Actually you need to collect some data during each calibration temperature that you can store on the chip and use it at the end of the calibration to compute the optimal settings.
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Q:
What is the difference between the MLX90320 and the MLX90326?
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A:
the MLX90326 is more or less the same as the MLX90320, the major difference is related to the automotive requirements. The MLX90320 is foreseen for reverse and over voltage protections, which is not the case for the MLX90326.
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Q:
What is the difference between the MLX90323 and the MLX90314?
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A:
The MLX90323 is designed to work in industrial applications. The temperature range is smaller then the one for the MLX90314 (-40 to 125).
Furthermore the MLX90323 has only a current output while the MLX90314 can also be programmed with a voltage output.
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Q:
I'm going to use a 90320 with a 5V supply and an output range 0,5 to 4,5 V. In my application the transducer bridge has a separate 15V ref supply. I can reduce the ref supply by a resistor to keep output voltage of the bridge in the 90320 input range (about 3 V). Is this ok ? Do you have any hint or schematics with a ratiometric out verse a separate ref supply ?
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A:
We advice you to keep the input range between 2-3V. To work ratiometric, the bridge needs to have the same supply then chip, otherwise it is not possible to work ratiometric.
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Q:
We are preparing for production with MLX90308 based 4-20mA sensors. We are looking for production level calibration software which will allow calibration of 10 x sensors at the same time. Basically we like to bring 10 x sensors to low pressure, set Zero than bring the whole manafold to High pressure and set Span. Does anyone developed MLX90308 calibration software which can handle 10 x sensors at the same time?
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A:
Is this a voltage or a 4-20 mA output application?
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A:
It is 4 - 20mA (2 wire) application. Hazardous area pressure sensors for CAT C7 industrial engine.
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Q:
I am trying to determine if I can use the MLX90308 with a load cell. The cell is a 350ohm cell with 2mV/V output at full scale. Ideally I will use the device in current mode. Is this the correct device?
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A:
First you need to determine what supply voltage you expect for your load cell. With the MLX90308 you will supply your cell with 5V and it will take too much current with a 350ohm cell. The MLX90314 is the same as the MLX90308 besides that it has a much higher gain (2625mA/V max).
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