Hi there.
I'm planning on working with the TGS5141 carbon monoxide sensor (datasheet attached).
In the datasheet I read the following:
xxxx = sensor's sensitivity (slope) in numeric value as
determined by measuring the sensor's output in
300ppm of CO (Ex.1827=1.827nA/ppm)
In this example, this particular sensor gave an output at 1.827nA per ppm measured at 300ppm which would then translate to 548.1nA (0.5481uA) at 300ppm. The opamp then amplifies this small current into an output voltage. I assume the 1M resistor in the diagram should be a low tolerance resistor (maybe trimpot), I guess this in combination with the sensor is maybe part of a voltage divider?
Is there any way to know the output voltage from the opamp at 300ppm (based on the known configuration and nA per ppm)
I guess this depends on the used opamp and that the conversion ratio for nA to V may be in the datasheet for the opamp, is that correct?
The circuit mentions the use of the AD708, I didn't find many suppliers for this one on Aliexpress and had a look at the LF356N (datasheet attached) which requires according to the datasheet a low input bias current of 30pA. As in this example we have 1.827nA per ppm, 30pA would be sufficient right? Or did I misunderstood the the function of input bias current?
I have serious trouble in figuring out the output voltage from the opamp at 300ppm. I looked at some online calculators but they all seem to ask for input voltage and the datasheet for this sensor only mentions a certain uA at 300ppm. Could anyone shine some light on this as I would like to understand how to this conversion is calculated.
All help is appreciated
I'm planning on working with the TGS5141 carbon monoxide sensor (datasheet attached).
In the datasheet I read the following:
xxxx = sensor's sensitivity (slope) in numeric value as
determined by measuring the sensor's output in
300ppm of CO (Ex.1827=1.827nA/ppm)
In this example, this particular sensor gave an output at 1.827nA per ppm measured at 300ppm which would then translate to 548.1nA (0.5481uA) at 300ppm. The opamp then amplifies this small current into an output voltage. I assume the 1M resistor in the diagram should be a low tolerance resistor (maybe trimpot), I guess this in combination with the sensor is maybe part of a voltage divider?
Is there any way to know the output voltage from the opamp at 300ppm (based on the known configuration and nA per ppm)
I guess this depends on the used opamp and that the conversion ratio for nA to V may be in the datasheet for the opamp, is that correct?
The circuit mentions the use of the AD708, I didn't find many suppliers for this one on Aliexpress and had a look at the LF356N (datasheet attached) which requires according to the datasheet a low input bias current of 30pA. As in this example we have 1.827nA per ppm, 30pA would be sufficient right? Or did I misunderstood the the function of input bias current?
I have serious trouble in figuring out the output voltage from the opamp at 300ppm. I looked at some online calculators but they all seem to ask for input voltage and the datasheet for this sensor only mentions a certain uA at 300ppm. Could anyone shine some light on this as I would like to understand how to this conversion is calculated.
All help is appreciated
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