Low voltage voltmeter + wireless network

[frankvetrano]

Hello everybod,
I am an italian researcher on signal processing. Currently I must carry on a study on small voltage (at least 50 mvolts resolution) measurements on dis-omogeneous ground for agriculture applications. My idea is to use a a wireless network sensor with 5-6 nodes. Each nodes should acquire the above voltage and to transmit this measurement to the server. I would like to use a simple and robust voltmeter ( I am conscious that the voltage signal will be very noisy), an AC/DC converter (es. MCP3208) which give the digital voltage measurement to a node wireless (Texas CC2480) or any kind of network sensor.
Would anybody suggest me how to do this ?
Thank you so much in Advance.
Cordially,
Frank

 

[dark]

Hello everybod,
I am an italian researcher on signal processing. Currently I must carry on a study on small voltage (at least 50 mvolts resolution) measurements on dis-omogeneous ground for agriculture applications. My idea is to use a a wireless network sensor with 5-6 nodes. Each nodes should acquire the above voltage and to transmit this measurement to the server. I would like to use a simple and robust voltmeter ( I am conscious that the voltage signal will be very noisy), an AC/DC converter (es. MCP3208) which give the digital voltage measurement to a node wireless (Texas CC2480) or any kind of network sensor.
Would anybody suggest me how to do this ?
Thank you so much in Advance.
Cordially,
Frank

Do not forget to use Differential amplifiers before measurement , else you might be lost . After buffering you may use any adc 12bit or more to do your job.

-Adi

 

[frankvetrano]

Thank you for your suggestion. Do you know any commercial device in order to implement this low voltage voltmeter?

 

[blueroomelectronics]

How do you plan on powering the wireless sensor? What range do you need?

 

[frankvetrano]

Hello Bill,
thank you for your message.
The wireless sensor kit I am going to use is supplyed by batteries rechargeable by photovoltaic modules. Unfortunatelly the wireless nodes I have found untill now needs a signal of amplitude equal or greater then 0.1 volts. I need to do a simple voltmeter to measure small dynamics (50mvolts) + a A/D converter whose output (voltage measurement) goes to the wireless node...
It may be simple..but I have some difficulties....

 

[blueroomelectronics]

Can you tell us the model of sender?

Edit, ahh a ZigBee. Have you looked at the XBee modules? You can build a preamp to get the signal levels you need.

 

[frankvetrano]

Hi Bill, currently I have to describe the project and all the components that I will use in my research. I have considered the Eko Pro Series (by crossbow technology) and other kits such as the Texas Instrument Demonstration kit eZ430-RF2480. If you have any suggestion, please tell me. I should describe all the devices with the corresponding price within few days, in order to have the grant (money) to buy everything. The budget approximately is around 3.000 euro (three thousand) ...not so much because this is a preliminary research project. I think in this topic you are very skilled, so please if you have time suggest me how to proceed. Now I am going to sleep...it is almost middle night. Talk you soon, Frank.

 

[blueroomelectronics]

Well the xbee modules are cheap enough at $20 US and have an AD input that combined with an amp should do the trick.

 

[dark]

Thank you for your suggestion. Do you know any commercial device in order to implement this low voltage voltmeter?

Frank please let us know from where the signal is comming from(Sensor?) .

-Adi

 

[dark]

Well the xbee modules are cheap enough at $20 US and have an AD input that combined with an amp should do the trick.

Bill Zigbees are not heavy duty product , I have used them for industrial application and none worked . My personal experience with Xbeepro is very disheartning the way they collapse in industrial environments .I have also used high dB amplifiers with these but no use , the noise level tends to be very high distorting the signal . Though Xbeepro /Xbee are nice candidates for in room/low db applications at almost room temperatures.

-Adi

 

[frankvetrano]

Good morning Adi, thank you for helping me. The voltage signal (low voltage) comes from the telluric ground with different PH. I will put two probes in the ground to acquire the voltage (I need a resolution of at least 50 mvolts). The voltage, converted to digital signal, should be acquired by the wireless node. Because I need in the same region to acquire temperature and moisture too, I was thinking to use the microchip MCP3208 whose output should go to a network processor (node) such as the CC2480 (ZigBee protocol). What do you think about ? First of all I need an high impedance circuit to implement the voltmeter....

 

[dark]

Good morning Adi, thank you for helping me. The voltage signal (low voltage) comes from the telluric ground with different PH. I will put two probes in the ground to acquire the voltage (I need a resolution of at least 50 mvolts). The voltage, converted to digital signal, should be acquired by the wireless node. Because I need in the same region to acquire temperature and moisture too, I was thinking to use the microchip MCP3208 whose output should go to a network processor (node) such as the CC2480 (ZigBee protocol). What do you think about ? First of all I need an high impedance circuit to implement the voltmeter....

Frank , what type of electrodes you are using for the measurement? . It would be quite difficult to get accurate reading I would guess, due to the relative un certainity of the process involved . I would use an Instrumentation amplifier with very high input impedance as you know the electrodes are un referenced . You must use MCP3201 instead as it has differential inputs . Check it out if it fits best for your application without Instrumentation amplifier? .

 

[frankvetrano]

Merry Christmas !!

Hello, before all, MERRY CHRISTMAS to Every body !!!
Dear Adi, for my experiment I am planning to use Platinum electrodes.
Thank you for suggesting me to use MCP3201..I'm just checking its datasheet. I hope to do something working acquiring this low voltage signal.
Best regards, Frank.

 

[frankvetrano]

Hello every body, regarding the low voltage voltmeter, could anybody tell me where I can found the circuital scheme ? I don't need any display or led for measures visualization, just to acquire the data will passed to an A/D converter such as the MPC3201 (as suggested to me). Thank you so much. Have a good time, Frank.