Research on Principle and Method of Active Power Measurement Based on Power Analyzer

1 Introduction

Industrial applications are basic but important for the measurement of voltage and current. Industrial pressure, temperature, humidity, etc. Many measurements use sensors to convert physical signals into voltages or currents, and then display them on the meter after being analyzed by electronic instruments. Therefore, how to measure accurate voltages and currents is very important. This article mainly introduces the application of HYCON HY16F198B Series chip in voltage and current measurement.

Because the HY16F198B chip integrates a high ΣΔ ADC, and the ADC output frequency can reach 10kHz, and with the internal hardware LCD driver, it has a very high accuracy when the HY16F198B is used for voltage and current measurement.

2. Principle explanation

2.1. Measuring principle:

Based on the HY16F198B chip to realize the application design of voltage and current measuring meters

2.1.1. Voltage measurement:

The circuit diagram is shown in Figure 1. This circuit is a simple voltage divider circuit with a voltage divider ratio of 20:1. Due to the program setting, the voltage difference between AIO0 and AIO1 is 1.2V. Therefore, the upper limit of the measurement voltage is 20V.

2.1.2. Current measurement:

The circuit diagram is shown in Figure 2. The division method is that when a current source flows through a 10Ω resistor, a voltage difference is generated. Reverse the current flow through the method of measuring the voltage difference.

The resolution is divided into external resolution and internal resolution. The external resolution is the ratio of the measured output voltage value to the voltage value that needs to be identified. The measured voltage value for this application is 10mV.

Generally, the internal resolution determined by our visual method usually means that when the LCD display has only 1 division after the software is processed, the number of full-scale divisions at this time is the internal resolution, and the signal represented by 1 division is about 2 3 times RMS Noise.

The smaller the ratio of internal and external resolution, the higher the voltage and current meter, but the ratio of internal and external resolution is limited. For example, if the full-scale differential pressure is 1.1V, to achieve 2000 Count, a voltage and current meter with an internal and external ratio of 1:10, if the signal is not amplified, the signal to be processed is 1.1V/(2000×10)=55uV. The HY16F198B ADC can handle a signal value of approximately 65nV, so it is easy and accurate to complete the measurement and display of this specification.

Whether the ADC performance can meet the specification requirements, it is usually estimated by RMS Noise whether the internal resolution ratio is stable or not. For the development of electronic products, the bottleneck of the internal resolution that can be achieved by using the HY16F198B chip is the Input RMS Noise rather than the ADC resolution. HY16F198B ADC signal to be measured is amplified by PGA and AD magnification adjuster (PGA=32, ADGN=4), under the condition of OSR=32768 outputting 10 ADC values per second, its Input RMS Noise is about 65nV, But because its Input Noise is mainly composed of Thermal Noise, if we use average software processing, we can further reduce Input Noise.

If we averagely process the Input RMS Noise of 8 pens and take into account other noise factors, it can reach about 40nV, and 3 times the RMS Noise represents about 1 grid of scrolling, which is 120nV. When using 2.4V driving voltage, the voltage difference can reach 2.4mV at a full scale of 1mV/V, so in this case we can get an internal resolution of 20000 Counts.

2.2. Control chip

Introduction to MCU: HY16F series 32-bit high-performance Flash MCU (HY16F198B)

HY16F series 32-bit high-performance Flash MCU (HY16F198B)

Features description:

(1) Adopt Andes 32-bit CPU N801 processor.

(2) The voltage operating range is 2.2~3.6V, and the operating temperature range is -40℃~85℃.

(3) Support external 16MHz quartz oscillator or internal 16MHz high RC oscillator.

（3.1）Operation mode 0.6mA@2MHz/2

(3.2) Standby Mode 5uA@ LSRC=34KHz+IDLE Mode

（3.3）sleep mode 2.5uA

(4) Program memory 64KB Flash ROM

(5) Data memory 8KB SRAM

(6) With BOR and WDT functions, it can prevent the CPU from crashing.

(7) 24-bit high-precision ΣΔADC analog-to-digital converter

(7.1) Built-in PGA (Programmable Gain Amplifier) can be up to 128 times magnification.

(7.2) Built-in temperature sensor TPS.

(8) Ultra-low input noise operational amplifier OPAMP.

(9) 16-bit Timer A

(10) 16-bit TImer B module with PWM waveform generation function

(11) 16-bit TImer C module with digital Capture/Compare function

（12）Hardware serial communication SPI module

（13）Hardware serial communication I2C module

（14）Hardware serial communication UART module

(15) Hardware RTC clock function module

（16）Hardware Touch KEY function module

(17) Hardware LCD Driver 4x36, 6x34

3. System design

3.1. Hardware description

Use HY16F198B built-in ADC with external circuit for voltage and current measurement. The whole circuit contains two buttons, namely (mode selection) and (measurement) button part, with the internal hardware LCD Driver to display the measurement value.

(A) MCU: HY16F198B

(B) Display mode: HY16F198B internal hardware driver 4x36 LCD (LCD Driver Segment 4X36)

(C) Power circuit: 5.0V to 3.3V power system

(D) Analog sensing module: internal ADC

(E) The connection circuit of online programming and ICE, through the connection of EDM, can support online programming simulation.

and has a powerful C platform IDE and HYCON analog software analysis tools and GUI support.

3.2. Function description

The PGA inside the ADC is amplified by 1 time, and the ADGN is amplified by 1 time. The reference voltage is supplied by VDDA -VSS, then ΔVR_I=1.2V.

3.2.1. Voltage measurement

In voltage measurement mode, the measurement range is ±20V, with a voltage measurement circuit. Display to 1mV, accuracy to 10mV.

3.2.2. Current measurement

The main range of current measurement is ±110mA, with current measurement circuit. Both display and measurement accuracy are 0.1mA

4. Operation process

4.1. Operation method

After starting, first turn on the LCD, then initialize and display Hycon. Then skip to mode selection.

4.1.1. Button control instructions

Through S2 (mode button) to switch the measurement mode; S3 (measurement button) represents the start of measurement.

and Buzzer will make a sound every time you press the key.

4.1.2. Measuring voltage mode

20V means ±20V measurement (with external measurement circuit)

4.1.3. Measuring current mode

110mA means ±110mA measurement (with external measurement circuit)

4.2. Program flow

4.2.1. Main Loop flow chart:

4.2.2. Key processing flowchart:

4.2.3. LCD display processing flow chart:

5. Technical specifications

(1) VDD=3.3V

(2) Power consumption: about 2.24mA in working mode (HAO=4MHz, ADC Enable)

(3) Measurement accuracy: voltage 10 (mV) and current 0.1 (mA)

（4） Applicable scope: measuring voltage range (± 20V)

Measuring current range (± 110mA)

(5) Working temperature: -40℃~ +85℃

6. Summary of results

The HY16F198B is used as the main control unit, combined with internal high-frequency, multi-channel input, and fast ADC measurement. Regardless of the voltage or current measurement, compared with the commercial electric meters, not only the power consumption is lower than the general commercial electric meters, but also the accuracy is not lower than that of the commercial electric meters. The internal ADC of HY16F198B can not only be used to measure voltage and current, but also can be combined with external sensors for other measurements, and it still has a pretty good performance.