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Generic 3 Channel Isolation Amplifier
The DRA range are DIN Rail mounting generic 3 channel isolation amplifier that can be configured during manufacture. Standard options are offered with 3 types of inputs, External Current Shunt, Internal Current Shunt and Internal Voltage Divider. It can also be offered as a customised unit with the input scaling and configuration defined by the user.
Isolation
The DRA004 PCB isolates the input channels from each other and from the common output circuit. The output circuit is referenced to 0V on J6 and the input circuits have their supplies IsoDC that generate references 0VA1, 0VA2 and 0VA3. The isolation amplifier IsoAmp is approved to IEC 60747-5-5 1414Vpeak working insulation voltage.
Input
On each input there is a network of resistors that are defined in detail below.
Output, Scaling and Power Supply
The output of the DRA004 circuit is compatible with National Instruments’ DAQ modules with a range of ±2.0V around Vref which is internally connected to 0V. The standard gains for GainAmp convert ±50mV or ±200mV input to IsoAmp to ±2.0V output. Different gains and calibration can be set by the factory by adjustment of RG. There is a RC filter that limits the bandwidth to 80 kHz and the output buffer can drive a capacitive load.
Customisation
The Input Network is offered in standard configurations as detailed below but clients can request other scaling and supply configurations. For example a customised unit can run from a single 5V supply with an external Vref. The unit can be scaled up to ±200mV on the IsoAmp and to ±4.8V on the output.
Input Network Standard Variants
Custom (Voltage and Current Measurement)
The input network can be factory built to suit the user on request. The PCB has the following limitations:
The gain of GainAmp, see Fig 1, can be set by RG on each channel for custom scaling.
* ±200mV is the maximum measurable input to the isolation amplifier. ±2V is the maximum without damage and ±6V is maximum transient for 2secs.
Mechanical
The DRA004 and variants are packaged in a DIN rail housing from Phoenix, type ME MAX 22,5 G 3-3 KMGY with connectors MKDSO 2,5/4-6 SET KMGY.
Conformance
Product Variants - DRA005 – 3 channel external current shunt. (±50mV)
Product Variants - DRA006 – 3 channel internal current shunt. (±20A)
Product Variants - DRA007 – 3 channel voltage. (±1000V)
Product Variants - DRA008 – Single phase voltage and external current shunt. (±1000V and ±50mV)
Product Variants - DRA009 – Single phase voltage and internal current shunt. (±1000V and ±20A)
