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Last Post 04/18/2012 10:30 AM by  Samuel Fonseca Soto
Accuracy and time response CR4100 and CR2DARL-500
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Samuel Fonseca Soto
New Member
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Posts:2


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04/17/2012 2:30 PM
    We are setting up a power logging station and we would like to know if we would get better accuracy and better response time with a CR4470 than a metering current transformer CR2DARL-500?
    We are able to read 0-10 VDC or up to 5A signals.
    Any of the monitored equipment will be consuming more than 30A.

    Any orientation will be appreciated.
    Tony Hodges
    CRM Staff
    Basic Member
    Basic Member
    Posts:154


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    04/18/2012 8:49 AM
    Dear Sir,

    Thank you for your interest in our product lines. The CR4400 series has a basic accuracy of 0.5% at full scale. For a 5 volt output, that would be 5 VDC +/- 25 mVDC. For a 30 amp reading, the output would be 3 VDC +/- 25 mVDC, or .83% accurate at 30 Amps in. Since this is a transducer, the response time is 250 mS. Please note that the CR4400 series is an average sensing model, meaning it is calibrated at 60 Hz. Different frequencies will exhibit a different response. For multi-frequency sensing, please use the CR4100 series True RMS units.

    For the CR2DARL-500, this is a current transformer with an accuracy of 4.8% at a 0.1 ohm burden. This accuracy will be maintained down to 10% of rated, or 5 amps. Obviously since this is a CT, the response is practically instantaneous. However, the output is an AC current, so developing a dc voltage or a reading from a 60 Hz waveform will require similar filtering and response delay circuitry to obtain a useful signal. The accuracy is poor because this is a 5 amp output unit, and the CT uses only 10 turns on the secondary, which is minimal magnetic linkage.

    The CR4400 series uses an internal high turn ratio, high accuracy CT. Other off the shelf CTs offered by CR Magnetics can improve the accuracy if a CT is chosen.
    Samuel Fonseca Soto
    New Member
    New Member
    Posts:2


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    04/18/2012 10:30 AM
    Thank you for your response!

    I have an additional question:

    When you refer to a shelf CT, what series of shelf CTs you offer could be an example of an improved accuracy CT?

    Another detail is that if we decide to use a CT we would be reading the current signal directly with a NI 9227 module with a 24 bit resolution , a sample rate of 50KS/s, an input current range of +/- 5Arms (14A peak), an maximum current range of 0.011mA accuracy and a 12mOhm input impedance.
    Would the accuracy of the CT vary due to the input impedance of this module?

    Thank you once again for your assistance!


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