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pressure sensor help

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abbasogur

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hello every one
iam new here and my english is not good so plase Be patient with me . i have a presure sensor(mpx200a) and i wont to connect it to a bottom of water tank but the problem is i don't know which side i will use for measuring the pressure also i wonder if it need any amplifire or not
plase help
plase help
with my respect
 
i don't know which side i will use for measuring the pressure
Use port P1 (read the datasheet).

i wonder if it need any amplifire
The full scale output is 60mV (read the datasheet).
So, depending on what you want to do with the signal from the pressure transducer, you may need an amplifier.

JimB
 
Thank you for reply jim and i wont this signal for controlling to water level in the tank by using a microcontroller (pic16f877a) and i will do that by making a counter İn adc the . İs this voltage enough for the microcontroller or not
With my respect
 
İs this voltage enough for the microcontroller or not
What does the datasheet for the 16F877 say?
I have not read that datasheet but assume that it is similar to the 16F887.

The 16F887 can use the 5volt supply as a reference for the ADC, or, an external supply.

If you use the 5v supply as a reference, the resolution of the ADC will be 5.00v divided by 1024bits which is 4.88mV.
This is not going to give very good control for your watertank.

You could use a much lower voltage for the ADC reference, say 100mV.
This would give a resolution of 0.097mV. This would be much better, but working at low signal levels you could have problems with noise and interference on the signal lines.

If I were doing this project, I would uses an amplifier for the signal and I would put that amplifier as close to the transducer as possible in order to minimise noise pick-up on the signal lines.

JimB
 
hi abba,

For a 60mV signal you will have to amplify it before the ADC input.

If you check the d/s for 16F877 you will see that the external Vref cannot be less than approx +2.5V.

There are a number of OPA's available that will work from a single +5v supply
 
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If you check the d/s for 16F877 you will see that the external Vref cannot be less than approx +2.5V.
A good point Eric.

I had wondered if there was a limit on the reference voltage, but could not see it in the section on ADC operation. (It is in Electrical Specifications).

Also, while we are talking about a 60mV signal, this is just the full scale output of the MPX200A which will measure up to 2 Bar pressure, (29psi in old money).
This corresponds to a head of liquid (water) of 20metres. Now that would be some big water tank.

I guess that the OPs water tank is a lot shorter that 20 metres and so the pressure will be much less, and so the transducer output will also be correspondingly lower.

JimB
 
hello every one
Thank you so much for answering my question . and sorry becouse i did not mention that the size will be 40 cm . also i will try to put a transistor 2n2222A338 for the sensor is this a good way or not .
thx again
 
hello every one
Thank you so much for answering my question . and sorry becouse i did not mention that the size will be 40 cm . also i will try to put a transistor 2n2222A338 for the sensor is this a good way or not .
thx again

hi,
If I understand correctly, the sensor is a 20 metres sensor which gives an output of 60mV and you have a water depth of 0.4 metres.

That will mean the maximum output will be [0.4/20]*60= 1.2mVolt

Would you please confirm that.;)

E.
 
yes as you said the pressure will be very low and i wont to take it as a feedback for the microcontroller chip .
with my respect
 
hello every body i change the pressure sensor and i used mpx7050d insted of mpx200a but the change in the sensor is very small what shoud i do for this problem plase help and the water tank high is 30 cm
 
Instead of just selecting some random pressure transducer and asking if it is suitable, why don't you learn how to calculate the pressure produced by a head of liquid?

View attachment 65400

Look at the attachment.

The pressure at the bottom of a column of liquid is given by the expression P = ρ x g x h

where:
ρ is the density of the fluid in kg/m^3 (freshwater is 1000 kg/m^3)

g is the acceleration due to gravity = 9.81 m.s^-2

h is the height of the fluid column in metres

P is the pressure in Pascal.

JimB
 
pressure sensor amplifier help

hello every one
i have project that i control to the level of water in the Bottle having length 30 cm and i using for that pressure sensor (mpx7050d) but the problem is the out put of it about 4.55 when its empty but when i add a water to the Bottle the pressure sensor is not read at all , but when i Squeeze the bottle the pressure sensor read about 4.57 , then i used an amplifier as the picture
**broken link removed**

but also the change is not appear what should i do
regard
 
Now my opinion is you need a Better Op-Amp.
Use an Op-Amp that has a Dual +/- Power Supply.
The LM324 can't give a Zero Ouput.
 
Hello every one i try this amp and i could see the change in the sensor when i add 30 cm of water and its about 1.5mv is this normal and what should i do to amplify this 1.5mv

Regard
 
Hello every one i try this amp and i could see the change in the sensor when i add 30 cm of water and its about 1.5mv is this normal and what should i do to amplify this 1.5mv

Regard

Use an Op-Amp that has a Dual +/- Power Supply.
The LM324 can't give a Zero Ouput.

Possibly use a TL071 or TL081 Op-Amp
 
Hi abba,

for your application I recommend to use an MPX2010DP. It has a full output voltage of 25mV at max span of 10KPa and can be used for measurement for respiratory diagnosis.

You must use a dual port sensor (suffix DP) to compensate for air density changes as well as temperature changes. The negative pressure port must be exposed to the open air. For least pressure loss in the pressure hose (positive pressure port) use PU-hose 6mm (polyurethane 6mm outer diameter/4mm inner diameter), available at Festo Pneumatik.

Ideally the MPX2010DP puts out a linear voltage of max 25mV.

Here is a precision amplifier connected to the MPX2050DP which I use to measure water tank level precisely to 10mm

It contains an instrumentation amplifier (INA111), a precision constant current source and two precision burden resistors (R1 and R2) to gain a precision reference voltage for offset compensation (±10mV).

If interested in the Eagle files PM your full name and email address.

Boncuk
 
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Why are you persistently using an LM324 for a precision requiring amplifier? Additionally the LM324 produces lots of noise!

Use an instrumentation amplifier like the INA111 and an offset amplifier like the OPA177 for your project.

An Arduino is a microprocessor, similar to any PIC with an A/D converter. The Arduino offers 10 bit A/D conversion.

Your offset amplifier must generate 800mV offset voltage with a usable full range swing of 2,500mV

Boncuk
 
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