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I am using a LEM HAIS 200-P and I never have worked with Open Loop current sensors before.

I have some questions about the datasheet:

  1. What is the difference between Primary nominal RMS current and Primary current measuring range?
  2. If I can force some Vref, so how's the offset fixed? It will change as I force the Vref, right?
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What is the difference between Primary nominal RMS current and Primary current measuring range?

Both are per-part number metrics. They both relate to full scale measurement range for a device. "Primary nominal RMS current" is the recommended max RMS current. It is also used in the equation for VOUT. "Primary current measuring range" is the max DC current that can be resolved.

If I can force some Vref, so how's the offset fixed? It will change as I force the Vref, right?

The datasheet indicates that you can force VREF to be between 1.5V and 2.8V; it is nominally 2.5V. VOE is defined as VREF +/- 0.025V, so yes, as you change VREF you will change the output offset (VOE).

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  • \$\begingroup\$ But the application notes says it's fixed offset..amds4.com.br/web/img/CH24108E_US.pdf \$\endgroup\$
    – mFeinstein
    Dec 24 '12 at 21:30
  • \$\begingroup\$ So if I am only working with DC current, how's the output formula? Ipn = Ip, so Ipn*Tp will always be equal to 1? \$\endgroup\$
    – mFeinstein
    Dec 24 '12 at 21:31
  • \$\begingroup\$ Could you point out exactly where the app notes indicate fixed offset? This would seem to contradict the datasheet. In your second follow-up question, what's Tp? \$\endgroup\$
    – HikeOnPast
    Dec 25 '12 at 6:22
  • \$\begingroup\$ Sorry..it was kinda late in here...I made a typo..it was supposed to be "Ipn/Ip". In page number 9 you can read "Gain and offset are fixed." (search for it using Ctr+F, it's easier) \$\endgroup\$
    – mFeinstein
    Dec 25 '12 at 6:30
  • \$\begingroup\$ That application note is specific to the HSX models, which are different from the datasheet you posted. \$\endgroup\$
    – HikeOnPast
    Dec 26 '12 at 16:01

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