Water Tank Depth Sensor problem...

[Mr HG]

Hello Mr Reloadron, The INA is not damaged but there is a little problem in the offset which is negative. the STM32 microcontroller accepts this negative voltage according his datasheet.

https://www.electro-tech-online.com/attachments/aaesp01-gif.84270/

The MPX2010DP with INA114 presents a good way to mesure level with precision... Thank you

Regards.

 

[Reloadron]

If everything works and there is just the negative offset I would scale the micro controller accordingly and go with it. As long as you are seeing the INA output change proportional to the pressure sensor output.

Ron

 

[KeepItSimpleStupid]

As was said the 324 is a BAD choice, We haven't seen your INA IA circuit. What people forget is to add some resistance to the inputs if there isn;t any inherent ones, The bias current has to have something to drop across. If there is a very low resistance path, you end up with very large offsets. This is a real world problem. For a theoretical op amp, the problem doesn't exist.

I recently responded to another thread with a similar problem. For an OP amp input, you can put any resistor inseries with the inputs without affecting the OP amp, except the higher the resistance, the lower the error and the greater noise. I've used resistors from 1 to 10K.

 

[rumpfy]

HG,
I have been watching yr progress and progress has been good.
However, your trouble started when you changed the supply from +/-12 Volt to +/- 14 volt. it is not clear to me how you are powering your MPX. From memory, these transducers are specified at 10 volt and are nulled at this supply voltage. They have a maximum supply voltage of 16 volt from memory.
Is it possible you are supplying the MPX from the +14 volt supply? and this value of supply voltage is approaching the maximum?
I have a 'universal' digital readout unit, and this includes a 'LH0070' which is a 10 volt precision reference. This supply is available for driving bridge devices like your MPX.
Its just a thought that maybe you need to look at the supply which drives your MPX.
Hope this helps.

 

[Mr HG]

HG,
I have been watching yr progress and progress has been good.
However, your trouble started when you changed the supply from +/-12 Volt to +/- 14 volt. it is not clear to me how you are powering your MPX. From memory, these transducers are specified at 10 volt and are nulled at this supply voltage. They have a maximum supply voltage of 16 volt from memory.
Is it possible you are supplying the MPX from the +14 volt supply? and this value of supply voltage is approaching the maximum?
I have a 'universal' digital readout unit, and this includes a 'LH0070' which is a 10 volt precision reference. This supply is available for driving bridge devices like your MPX.
Its just a thought that maybe you need to look at the supply which drives your MPX.
Hope this helps.

rumpfy,

For the supply of the MPX (10V) I am using a regulator 7810, which convert +14V to +10V.

Thank you for your good advice

 

[Mr HG]

HG,
I have been watching yr progress and progress has been good.
However, your trouble started when you changed the supply from +/-12 Volt to +/- 14 volt. it is not clear to me how you are powering your MPX. From memory, these transducers are specified at 10 volt and are nulled at this supply voltage. They have a maximum supply voltage of 16 volt from memory.
Is it possible you are supplying the MPX from the +14 volt supply? and this value of supply voltage is approaching the maximum?
I have a 'universal' digital readout unit, and this includes a 'LH0070' which is a 10 volt precision reference. This supply is available for driving bridge devices like your MPX.
Its just a thought that maybe you need to look at the supply which drives your MPX.
Hope this helps.

I poseted here the circuit of the sensor with the amplifier . I didn't have the package of the INA114 in Eagle so I put the LM714.

Thank you

 

[Reloadron]

Good practice calls for decoupling caps 0.1 uF on the IA power pins. I don't see any. Also in your schematic I don't understand what I have marked up?

So you want to add some .1 uF caps on each IA pins 7 & 4 to Gnd as shown in the data sheet also see Figure 11 page 12 of the data sheet. That is how your transducer should be connected.

Ron

 

[Mr HG]

Thank you Mr reloadron,

I am working no with this circuit and it gives me a good results... But no I have an other problem!!! I put it in a new topic.

 

[Mr HG]

Hello Mr Reloadron, sorry I don't understand your answer :

So you want to add some .1 uF caps on each IA pins 7 & 4 to Gnd as shown in the data sheet also see Figure 11 page 12 of the data sheet. That is how your transducer should be connected.

Ron

Can you please help me about the problem of the noise in the output of my INA114 ?? Can I make a 100nF capacitor between the output and the GND ?? It can delete the noise ?? I should make also a 0.1 uF capacitor between pins 4 and 7 ?? they can minimise the noise ?? I need some ideas please

Than you ery much