Infrared telemetry system for battery performance under high-speed rotation

    Abstract: This paper introduces an infrared telemetry system that can accurately measure and record the supply voltage and noise values ​​under high-speed rotation. It provides a technical means with strong anti-interference ability and high measurement accuracy for testing thermal batteries and chemical batteries activated on high-speed rotating machines.

    Keywords: infrared telemetry battery high-speed rotating machine anti-interference

Accurate measurement of the power supply characteristics of batteries operating under high-speed rotation (such as chemical batteries, thermal batteries, solid batteries, etc.) is a very important but difficult event. At present, according to different signal transmission forms, detection methods include brush contact wired measurement, mercury current collector wired measurement and radio telemetry. However, the applicable testing range of these methods is limited, and they are not applicable to new high-speed rotating machines with strong electromagnetic interference. In order to meet the requirements for high-precision battery testing on new high-speed rotating machines, we developed a battery-powered characteristics infrared telemetry system and achieved good results.

1 Telemetry system structure

Since high-speed rotating machines produce extremely powerful electromagnetic interference during operation, anti-interference design has become the key to system design. Tests have shown that both the electromagnetic induction coupling method and the radio transmission method are severely interfered and cannot be used normally. We finally chose the infrared telemetry method and successfully solved the problem of strong electromagnetic field interference.

The telemetry system consists of three parts: measurement and modulation transmission circuit, pre-receiving amplifier circuit, and demodulation circuit, as shown in Figure 1. The measuring and transmitting circuit and the battery under test are mounted on a high-speed rotating machine and move randomly at high speed. The transmitting tube is on the axis of rotation and can continuously transmit output signals. The receiving circuit is fixed outside the rotating machine at a location suitable for receiving signals.

2 Hardware design of telemetry system

2.1 Battery signal measurement conversion circuit

This circuit is installed on a rotating machine and rotates together with the battery under test. The circuit is powered by the battery under test; the circuit board is sealed with foam material. The circuit principle is shown in Figure 2.

Since the DC voltage can reach up to 32V, while the voltage value Vpp of the AC noise signal is only 25mV, the amplitude difference is very different, so it is not suitable to convert within one range. Therefore, AC and DC measurement circuits are used respectively, so that the DC voltage can be attenuated according to the conversion relationship and the AC signal can be appropriately amplified.

In the circuit, IC1 uses the precision voltage regulator chip AD586 to power the downstream circuit, so that fluctuations in battery voltage will not affect the normal operation of the circuit, ensuring the stability of the transmitter circuit; the VF conversion chip IC2 uses the high-precision integrated circuit CD4046.

2.2 Receiving and demodulation filter circuit

Separating the optical signal reception, conversion, preamplification circuit and demodulation circuit is an important measure to improve the system's anti-interference ability; amplifying the photoelectrically converted electrical signal and then transmitting it over a long distance can keep the demodulation circuit away from high-speed rotation machine. The preamplifier circuit consists of three parts: optical signal reception and conversion, electrical signal amplification and shaping, and electrical signal output, as shown in Figure 3. This part of the circuit is sealed in a metal shell, which can effectively prevent interference from external electromagnetic fields. The output square wave signal is transmitted to the demodulation circuit through the shielded wire. The demodulation circuit can be divided into three parts: the reception shaping circuit, the phase-locked loop demodulation circuit, and the filter output circuit, as shown in Figure 4.

In order to meet the high-precision requirements of the test system, it is very important to perform high-frequency filtering on the demodulated signal. Therefore, the filter circuit uses a Butterwolf third-order low-pass filter, composed of LM358.

2.3 Anti-interference design

The anti-interference measures of the test system mainly include shielding and grounding methods, including adding filter capacitors on the circuit board, designing shielding layers, etc. Each part of the circuit board should be completely sealed with a metal box, and its input and output wires should be shielded wires. The metal box, the shielding of the wires, and the rotary machine housing must be grounded.

3 Results and technical indicators

The performance indicators of this system are as follows:

Infrared telemetry carrier center frequency: 210kHz

Measuring range: DC——0～32V; AC (peak-to-peak value)——0.025～1V

Frequency response range: 0.5～2000Hz

Maximum receiving distance: 30cm

Maximum receiving deflection angle: ±11°

Test distortion: ≤3%

Tests have proven that this system fully meets the design requirements and works stably and reliably. 4 system test

The test environment of this system is as follows:

One high-speed variable frequency electric rotating machine (72000rpm)

A certain type of fuze thermal battery

A set of battery infrared telemetry system

HP digital voltmeter

An HP digital oscilloscope

Some test results are shown in Table 1.

Table 1 DC transmission test table of battery infrared telemetry system

It can be concluded from the above test results:

System maximum transmission error: +94%

System minimum transmission error: -0.63%

System DC transmission formula: Y=kX+a

System AC transmission formula: Y=kX

Among them, Y is the output, X is the input, and k is the AC transmission system mean value.

From the results, we can get: k=0.319; a=-0.161

A large number of tests and applications have shown that the performance indicators of this test system fully meet the design requirements and achieve high-precision signal testing in strong electromagnetic interference environments. It has been widely used.