How to Amplify mV to V

Discussion in 'General Electronics Chat' started by shinn_33, Nov 17, 2014.

  1. shinn_33

    Thread Starter New Member

    Nov 17, 2014
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    the salesman sold our company Antenna Protection Unit with wrong output voltage range. The output was 1 mV per 1 kW and our antenna system has only 4 kW thus, 4 mV. This level is too low for the input of the Telemetry System which requires -10 VDC to +10 VDC. The supplier cannot replace the units (we have 3) hence, are not monitored remotely. The output is linear and i want to design a linear amp with a 30 dB gain. Any help will be highly appreciated.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Really? They can sell you the wrong unit but not the right one?

    Anyway, do you have any specs, datasheets, etc.? Available power source? Frequency of operation?
     
  3. shinn_33

    Thread Starter New Member

    Nov 17, 2014
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    They sold 9 units, only three (3) were wrong due to they choose the kW output range instead of W only.
    I tried to get the documentation from them but none.
    Since I will be interfacing the output of the unit to my telemetry, the spec for the telemetry are the following:
    -Remote Control System is supplied by Davicom (davicom.com) and I am using MAC-216
    --Analog INPUT (Unipolar); 3 voltage ranges: 2.5; 10; 40 VDC, Input Impedance: > 200 kohms;
    --frequency is 0 since this is DC voltage
    --power source will depend on the interface, either dual or single but better if single +12VDC.

    I will be building 6 circuits because I have 3 units each having 2 outputs separately.
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    DC cannot be broadcasted so you must have some carrier frequency - or you are using the word "antenna" for a device other than a 'normal' antenna.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Since the input offset of most opamps is in the mV range, you will have to go to some effort to trim out the initial offset. An instrumentation amp may this job easier...
     
  6. shinn_33

    Thread Starter New Member

    Nov 17, 2014
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    The output is the Aux output and using a Fluke DMM, i measured the DC output voltage which confirmed that the DC output is proportional to the
    what I am measuring is the AUX Output which is a DC voltage proportional to the measured RF power in the transmission line using directional couplers. These are the Forward Power and the Reflected Power. The unit measures both and calculates the VSWR and according to the desired tripping threshold will open the interlock in order to turn off the transmitter. Again, I am just interested in the AUX DC voltage as I am monitoring the system remotely just like the other 6 units. using a Fluke DMM, I measured the voltage to be according to the specs, 1 mV per 1 kW.
     
  7. shinn_33

    Thread Starter New Member

    Nov 17, 2014
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    And that is my problem....the DC output is 0 VDC if the transmitter is off and increases linearly with the transmitter output power....
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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  9. shinn_33

    Thread Starter New Member

    Nov 17, 2014
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    Thank you, I will try to build that circuit around the INA122 and i will be using a 200R for Rg that will give me a G=1005, and maybe using a +/-5VDC to +/-12VDC power supply will yield approximately an ideal op amp, i found that the offset of INA122PA is 500uV which is very good.
     
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