Equipment Overview

The signal conditioning box can convert various external power signals into data acquisition modules that can collect voltage signals within the range of ± 10V. The overall power supply adopts AC 220V 50HZ power supply, with high-precision and high stability secondary power supply configured internally. The AC 220V power supply is converted into auxiliary power supply of different specifications such as DC ± 24V and DC ± 15V. The signal conditioning box can be equipped with different functional conditioning modules, which can complete functional modules such as signal driving capability enhancement, signal attenuation, signal amplification, signal optoelectronic isolation, signal filtering, signal protection, etc.

It adopts a standard module+wiring method to achieve the overall integration of the above functions in a 4U standard rack chassis. Different signal conditioning functions are required, and corresponding conditioning modules can be installed. It can support the installation of up to 12 signal conditioning modules, and rails need to be arranged inside the chassis to facilitate the installation and disassembly of each conditioning module. The specific external structure is shown in the following figure.

Figure 1 Front view of signal conditioning box

The signal conditioning box adopts a standard shelving mechanism design, with a box height of 4U, width of 430mm, depth of 250mm, and an overall color of silver. It is necessary to ensure consistency in the size of the chassis, ensure mechanical strength, and be able to support the stacking and placement of multiple chassis. The front panel of the chassis is printed with product identification patterns or logos. The front panel is equipped with power control switches, status indicator lights, and other devices. It is necessary to consider the overall heat dissipation of the conditioning box to ensure its long-term stable and reliable operation.

Module design

The signal conditioning box adopts AC 220V power supply and is equipped with a light switch and safety protection function. The specific dimensions of the conditioning module are 3HP wide, 3U high, and 175mm deep. It is powered by a 2 * 32 core connector on the rear panel of the module. The power on, working status, and channel status of each module can be monitored through its panel. The front panel is equipped with a DB 78 connector, which serves as the input and output interface for signals.

The signal conditioning box supports a variety of signal conditioning units and functions, such as signal amplification, discrete three-state output, signal attenuation function, dry node signal acquisition, current to voltage conditioning, PWM output amplitude amplification circuit, etc.

Module Design - Signal Amplification and Conditioning Unit

The conventional analog output module only has the ability to output 0-10V DC voltage signals. If the required output voltage exceeds this range, an amplification circuit is needed to amplify the 0-10V analog signal and amplify the amplitude of the output voltage to the desired range. At the same time, the conventional output module outputs a current of 5mA and uses a high voltage/high current operational amplifier to enhance the driving current to 200mA. The operational amplifier integrates excellent low-level signal accuracy and high output voltage and current, with internal protection to prevent overheating and current overload. And provide accurate current limitation, limiting the output current to 200mA through a control signal of 0 to 150uA.

Module Design - Discrete Output (28V, Ground, and Open Tri State Output)

The output of the conventional digital output module is at TTL level, which cannot meet the needs of three-state output. A discrete variable conditioning unit has been designed, which uses Darlington transistors to enhance the driving ability of the output TTL level signal. It serves as the control terminal signal of the SMT DC 5V double pole double throw relay, with the COM terminal of the relay as the output, the NC terminal can be suspended or grounded, and the NO terminal can be connected to DC 28 voltage or ground. Merge the two outputs together to achieve three-state control of discrete output, achieving 28V, ground, and open three-state outputs. When using, first place both relays in the open state, and then execute the corresponding output control to effectively prevent hardware circuit short circuit faults caused by possible software misoperation. The system controls the output state of the digital quantity TTL to achieve the opening and closing control of the external relay, and to achieve the required 28V, ground, and open discrete output of the product.

Module Design - Analog Attenuation Adjustment

The conventional analog signal acquisition module has a collection range of ± 10V. If the measured voltage exceeds this range, a resistance voltage divider adjustment unit needs to be designed to attenuate the measured signal. Based on the current size of the load, the appropriate combination is selected