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
- Channel-to-Channel isolation
- 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).
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.
2. Voltage at CHANNEL_1_PIN_A with respect to CHANNEL_1_PIN_B should be measured (input) .Refer Figure:3
Figure:2 Channel as Bidirectional switch
Figure:3 Channel as Input
- Channel as Bidirectional switch (output) Configuration
a. Bidirectional Switch - Configuration # 1 (CURRENT FLOWS FROM PIN-A TO PIN-B)
Figure 4: Bidirectional Switch – Config:1
b. Bidirectional Switch - Configuration # 2 (CURRENT FLOWS FROM PIN-B TO PIN-A)
Figure 5: Bidirectional Switch – Config:2
c. Channel as Voltage Measurement (Input) Configuration
Figure 6: Voltage Measurement
Basically the requirement is as shown below
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
- Bidirectional Switch - Configuration # 1 (CURRENT FLOWS FROM PIN-A TO PIN-B) using ADE7912
2.Bidirectional Switch - Configuration # 2 (CURRENT FLOWS FROM PIN-B TO PIN-A) using ADE7912
3. Channel as Voltage Measurement (Input) Configuration using ADE7912
4.Channel as Voltage Measurement (Input) Configuration using ADE7912
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.
Kumara Chandru C