regarding ad737 IC

Dear All,

i  want to calculate RMS value of Sinusoidal 50Hz waveform. so, i thought  to use AD737 IC. but in the datasheet i have used evaluation board  circuit . it's not working shown in figure "picture 1" in attached figure and also i used figure29 of datasheet shown in "picture 2" in attched figure both  are not working.

so, i'm in great need of this. and i want to make use 1V RMS  measurement.

1V RMS mentioned in the datasheet means either peak-peak  or RMS value.

please, suggest the circuit to be used which will measure 1V rms , 50Hz sinewave.

i'm not getting any application circuit for AD737which is working. please help me.

Thanks  & Regards

  • Hello Shiva,

    1. We're sorry to hear that you're having a problem. The boards are tested prior to shipment and work when unpacked. Did you obtain one of our boards or did you build your own version?

    2. Your figure 1 schematic will provide the 1V conversion you are looking for. Please send me a schematic sketch showing how you connected your board so I can make sure it is correct.

    3. 1V as stated in the data sheet means 1V rms, not 1V pk-pk.

    4. Whem a 50Hz 1V rms sine wave is applied to the input, the output will be negative 1V dc (-1V dc)

    5. You must have the correct supply voltages.

    6. If using a dual supply, the supply voltage must exceed the peak voltage by about 1.25V (headroom), so the supply must be at least +/-3V if a dual supply is used. Try a higher supply voltage such as +/-5V to see if the part works correctly.

    7. If you use a dual supply, you may use ground (0V) as your reference, as shown in fig. 1,

    8. If you use a single supply such as fig 2, you must offset the reference by 1/2 the supply voltage as shown in the schematic. The eval board doesn't proved the means to do so.

    9. Be sure all the jumpers are inserted as shown in your fig. 1

    10. A useful trouble-shooting technique is to probe all the pins with a DMM to be sure the voltages are all proper.

    11. Be sure all equipment is connected properly and turned on.

    Let me know if there are more questions,

    Best regards,


  • Thanks for the reply,

    i am not knowing why i'm getting the result like this.

    anyway,  i attached multisim 11 file with this mail. just checkout. when i  simulate this even then i'm getting mV signal output irrespective of  signal.

    (0 -2)Vrms, 50Hz, sinewave input voltage
    device used : AD737 (RMS to DC Converter)
    i have simulated the circuit shown in page 8 of  application note 268 of attached doc using NI multisim component evaluator 11.0  Analog devices edition
    and multisim file is attcahed shown in jpeg file  and also attached ".ms11" file too.
    so, please check this circuit and reply me where i'm doing wrong.
    i have tested in this wave:
    step:1 initially i have adjusted R5 resistor inorder to nullify the offset by applying 0V input.
    step:2 after that i have applied 2V input signal , then also i'm getting only mV signal output and i have changed the resitor value R4 from 0 - 50kohm. even then i'm getting mV signal.
    the same thing happend when i check practically. then i got the software while seraching multisim componeny\t evaluator analog devices edition. then i simulated then also same result. then i thought there is some problem with the application circuit only.
    now i'm getting doubt, whether this IC is successfull or not and i have some dooubt on teh application circuits becuase, applications circuits has to work. but in case of AD737, i don't know no application circuit related to AD737 is working. i'm fed up with the IC. if i won't get solution, then i'm going to not use this IC in my application. it's better to quit then trying. i'm trying from past 25 days or so. i'm not getting any solution regarding this.
    if anyone is having the multisim component evaluator 11.0 analog device edition file(.ms11) which work according to my requirement. please, share the circuit.
    i'm in great need of this, please help me .
    Thanks & Regards
  • 0
    •  Analog Employees 
    on Aug 2, 2018 4:24 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin