CA 36

Potentiometer input conditioners

General

The CA-36 is an isolated conditioner with a potentiometer input. It enhances, filters, isolates and converts the signal to a level suitable for connection to the data acquisition system, Industrial PC, PLC or other measuring system.

The CA-36 family of insulation modules protects people and measuring equipment and disengage galvanic from eventual events that can occur on the sensor side or somewhere else within a measuring environment. The module input is protected against voltage levels and transients up to 250 Vrms.

The family of the CA-36 module can be mixed in the same application with other families of isolation modules. They can be plugged into the measuring system and disconnected from it without turning off the power (hot swapable).

The voltage level from the potentiometer is measured by a differential amplifier with low temperature drift, low offset and a very stable gain coefficient. Differential amplifier does not require input grounding. On the front of the module below the mask there are two multi-port trimmers for precise adjustment of the offset and the zero. Both values ​​are factory-set and the user can override them if there is a need to do so.

Potentiometric excitation is performed with a precision current source of typically 0.25 mA, which minimizes self-heating of the potentiometer. The primary side of the module is isolated from the secondary side of the module and both are isolated from the power source. Input differential amplifier does not require grounding.

Prices and models of CA-36

Characterisation

The central component of the module is a signal isolation transformer. Like most transformers, this has a primary and secondary side. Using this terminology, the input side of the module is the "primary side" and the output side of the module is called the "secondary side". A sensor connector is connected to the primary side of the module, and the secondary side of the module is connected to the data acquisition and measurement system, to the analog input module of the Industrial PC or PLC, to a panel meter or to another measurement system.

Transformer signal isolation uses a method of amplitude modulation to obtain linear, stable and reliable characteristics. This technique provides better results than the technique with digital or linear opto-scanners or a condenser isolation technique. The primary side of the module is galvanically isolated or "floating" in relation to the secondary side of the module and in relation to the el. power supply. The signal demodulator on the secondary side of the module restores the original signal, which is then filtered and buffered to achieve a low noise level and low impedance output signal.

The CA-36 Series Insulation Modules have a fifth-order filter built-in, with the first Anti-Aliasing pole located in the primary module circuit while the fourth-order filter is located on the secondary side of the isolation barrier. After the Anti-aliasing filtering, the signal is fed to the chopper level behind the specially designed micro transformer. In the secondary stage, behind the isolation barrier, the signal is demodulated and filtered again from the transmissions and interference. The output from the module can be, if necessary, a voltage or current signal.

The warranty period is 7 years and the service period is 10 years. It is delivered with a user manual in Serbian or English language and with a calibration list.

CA-36 with 110/220V AC power supply (option)

The base version of the CA-36 works with a standard DC power supply of 19 to 30V DC (24V DC nominal). However, if the application requires the power supply of a 220V AC coder, which is not a rare case, then the user can order a conditioner with the suffix A. This type of conditioner works with an AC voltage of 85 to 265V or with a DC voltage of 100 to 400V. These two power supplies make the CA-36 applicable in many situations. Some users use these conditioners in an environment that is powered by a 110V battery, or in elevated AC voltage conditions in transformer stations.

On this conditioner model, there are three terminals for connecting the power supply: L, N and GND (Picture on the left). The L should connect the phase, neutral to N, and  GND to the ground. Grounding, apart from the safety function, has the function of reducing the internal voltage unit oscillations, so it should be connected in any case. If the DC power supply is used, it must be connected to the L and N connectors (the order is not relevant).

Relay (option)

The isolation conditioner family CA-36 with the suffix R has a built-in relay with a working and quiet contact on the external terminals. The relay can switch on or off to 240V, 6A, and can be set to activate when the input size is greater than the specified value or when the input size is less than the set value. There is a working and quiet contact on the copies. The relay has a built-in hysteresis control that can be fine tuned with a precision multi-port trimmer potentiometer.

The only limitation for this version is that if it is used with 220V power supply (version with suffix A), the relay has only a working contact.

The setting of the relay activation level is performed by the potentiometer on the front of the conditioner. In order to avoid the oscillation of the relay when the input size is the same, the hysteresis is assigned to the device. Hysteresis in the first case, when the relay is activated and when the input is higher than the set value, indicates the size for how much the input size should be smaller than the specified size for activating the relay to turn it off. In the second case, it indicates how much the input size should be to be higher than the set to switch off the relay. Hysteresis can be set to 1% or 5% span with an internal jumper.

If the load is applied to the relay of the inductive character, it is necessary to add the "snubber" from the outside in parallel to the relay contacts. The values ​​of the supply components are calculated, but can also be determined empirically for the given application. Generally, even if the load is applied to the relay of the inductive type, a capacitor of 0.2 uF per line with a 10 Ohm resistor can be used. For optimum performance, the supply wheel must be calculated because this is the best way to optimally extinguish the spark at the relay.