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ADE-7912 For isolated DC Voltage and Current Measurement

Question asked by Kumara.chandruc1234 on Oct 15, 2015
Latest reply on Oct 19, 2015 by hmani

Hai Sir,

 

We are planning to design an isolated 50 Input/output Data Acquisition System, with I/O Channels individually isolated and used either as Input ( Voltage to be measured) or Bi-Directional Switch (output.Current to be measured).

 

External Field Bus Input is 0 to ±30V DC and the system should have

  1.     Channel-to-Channel isolation
  2.     Channel-to-System side isolation

 

Each I/O Channel has two pins, which should be connected to the external field side.

(e.g for channel-1  CHANNEL_1_PIN_A & CHANNEL_1_PIN_B).

 

 

1.jpg

                    Figure 1: Two pins per channel


Each Channel should either act as

 

      1.      Bidirectional switch (output)  i.e CHANNEL_1_PIN_A  to be shorted/Open to  CHANNEL_1_PIN_B. Refer Figure:2.Current                      need to be measured, when the channel acts as  a bidirectional switch.

 

                                              OR


2.  Voltage at CHANNEL_1_PIN_A with respect to CHANNEL_1_PIN_B should be measured (input) .Refer Figure:3


2.jpg

Figure:2 Channel as Bidirectional switch

 

3.jpg

Figure:3 Channel as Input

 

  1. Channel as Bidirectional switch (output) Configuration

a. Bidirectional Switch - Configuration # 1 (CURRENT FLOWS FROM PIN-A TO PIN-B)

4.jpg

Figure 4: Bidirectional Switch – Config:1


b. Bidirectional Switch - Configuration # 2 (CURRENT FLOWS FROM PIN-B TO PIN-A)

5.jpg

Figure 5: Bidirectional Switch – Config:2


c. Channel as Voltage Measurement (Input) Configuration


6.jpg

Figure 6: Voltage Measurement


Basically the requirement is as shown below

7.jpg

Figure 7: Requirements


The requirements are

1. Need an isolated SSR relay.  (To short/open  CHANNEL_1_PIN_A  to CHANNEL_1_PIN_B )

2. To measure the current. ( Which flows when CHANNEL_1_PIN_A  is shorted to CHANNEL_1_PIN_B)

3. To measure voltage at CHANNEL_1_PIN_A  w.r.t CHANNEL_1_PIN_B.

 

Requirement 1: can be accomplished using a SSR like LAA710 or ASSR-1530 (PhotoMos Solid State Relay).

I want to use ADE7912 for requirements 2 & 3.

 

I am attaching the circuitry using ADE-7912 for measuring current and voltage

 

  1. Bidirectional Switch - Configuration # 1 (CURRENT FLOWS FROM PIN-A TO PIN-B) using ADE7912

8.jpg

2.Bidirectional Switch - Configuration # 2 (CURRENT FLOWS FROM PIN-B TO PIN-A) using ADE7912

9.jpg

3. Channel as Voltage Measurement (Input) Configuration using ADE7912

10.jpg

4.Channel as Voltage Measurement (Input) Configuration using ADE7912

11.jpg

 

Thanks a lot for patiently going through the description.

 

Basically my doubts are,

 

1. Whether ADE-7912 can be used for DC voltage and DC current measurement?

2. The DC voltage is coming from an external system.It is either 0V or +27V.

3. As per datasheet I1P w.r.t IM should have a maximum voltage of +-31.25mV.V1P w.r.t VM should have a maximum voltage of +-500mV. So can i use for measuring current irrespective of direction of flow? (please refere first two figures?)

Can i reverse the polarity of DC input voltage and measure as +27v or -27v? (please refer  3. Channel as Voltage Measurement (Input) Configuration using ADE7912 & 4. Channel as Voltage Measurement (Input) Configuration using ADE7912)

 

Kindly go through the desciption and help me.Kindly ask me for further clarifications.

 

With Regards,

 

Kumara Chandru C

BEL,India

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