Digital Meter Design - New Trends in Digital Multiplexer Chips
2019-02-19 19:02:40
Abstract: Electronic motor personnel will use pointers or digital multiple meters (DMMs) for inspection or experimentation. In the past, portable digital instrumentation industry used Harris (has been acquired by Intersil), JRC. Digital analog meter converters (Analogto Digital Converters, ADCs) manufactured by foreign manufacturers, such as Maxim, Samsung, and Telcom (acquired by Microchip), convert input analog signals into digital signals for processing. The article mainly introduced the new trend of digital instrument design-digital multiplex table chip for everyone to understand.
I. Introduction:
Electronic motor personnel will use pointers and meters or Digital Multiple Meters (DMMs) during maintenance or experimentation. The past portable digital instrument industry used Harris (has been acquired by Intersil), JRC, and Maxim. Analog to Digital Converters (ADCs), which are manufactured by foreign manufacturers such as Samsung and Telcom (acquired by Microchip), convert input analog signals to digital signals for processing. However, the portable digital instrument industry is characterized by a small quantity, many types, and a long product life cycle. Therefore, these foreign integrated circuit manufacturers have no longer designed new A/D converters for digital multiplexed meters, and have even withdrawn from the market for A/D converters dedicated to digital multiplexed meters. The digital multiplex table requires only one chip plus resistors, capacitors, protection components, etc., to complete a product, so the threshold is not high, and the industry pie is so large that the end is the price war, and the profit is not as good as consumption. Sex products. For the digital multiplex table, the dedicated analog-to-digital converter is the core. Most of the portable instrument industry is relatively small, unlike Fluke, which can open its own dedicated DMM chip.
In recent years, the development of integrated circuits has been booming. There are several DMM-specific chip suppliers. There are two architectures in the analog-to-digital converters. They are Sigma-Delta and Dual Slop. For the architecture. This article will introduce the DMM dedicated chip of the Hycon HY12P65 mixed-signal processor (Mixed-Signal Microconductor), which uses a sigma-delta analog-to-digital converter architecture.
Second, the evolution of portable power meter:
The earliest portable power meter was a three-point meter. This generation of instruments has a low unit price, but it has low accuracy, low resolution, little functionality, and no input protection.
Since the beginning of the development of integrated circuits, chip vendors have designed analog-to-digital converters, so there are Handheld Manual Range Digital Multimeters, which use ICL7106, ICL7108, TLC7135, and HI-7159A analog digital. The converter, in addition to the voltage, resistance, and current measurements of the pointer triple-use meter, adds capacitance, frequency, and temperature, and the DMM manufacturer adds input protection circuitry. However, almost all functions require external circuit switching. When using it, the manual gear must be used to select the gear, which is inconvenient to use.
In order to simplify the operation, chip suppliers have designed DMM-specific analog-to-digital converters. Therefore, there are handheld automatic range digital multiple meters, and such meters use TelcomTC818A, SamsungKAD7001, and JRCNJU9210 analog-to-digital converters. In general, all the functions of the DMM are designed in the chip, as long as the resistance and capacitance are added, and the manual selection of the gear is not required in use.
However, users have new requirements such as high accuracy, high resolution, connection to a computer, or special features. Therefore, the chip supplier designs a component for the DMM dedicated analog front end (such as Maxim's MAX133/MAX134), or combines the analog front end with an MCU (such as Epson's S1C62M20), and the chip meets new requirements with the MCU. However, in addition to voltage, resistance, and current measurements, the chips of such products require additional functional circuits, which is not ideal.
In order to achieve the above new requirements, Fukang Technology has introduced a new generation of DMM-specific chips, such as HY12P65, to solve these problems.
Third, the chip new trend function overview:
In the future, the trend of the portable digital instrument industry must be to have its own product function planning in order to no longer be a price war. For example, an intelligent electric meter must rely on a more flexible DMM special chip. The new trends can be divided into the following categories according to their functions:
1. Switch network can be planned in the past DMM special chip will be fixed for each function and file bit switch network, the advantage is easy to design, but flexible switching multi-function network, can not have its own product function planning. The DMM special chip introduced in this article has a switchable network. If the domestic portable digital instrument industry, there is more room for product design.
â–²HY12P65Analog Switch Network
2. High resolution Σ-Δ analog-to-digital converter The DMM dedicated chip produced by foreign manufacturers in the past, A / D converters are used double slope integration as the framework, this architecture analog-to-digital converter conversion speed is slow, and used The quality of the integral capacitor affects the stability and the error of the entire converter. Usually the integral capacitor needs to use good materials such as MPE or MPP, and it is not easy to achieve high resolution.
The Σ-Δ analog digital signal converter has been used in more and more industrial control and advanced instrumentation in recent years. Its greatest advantage is its small number of peripheral circuits, high conversion speed, high resolution and accuracy, and it is less susceptible to power systems. For 50/60Hz and all effects, the unit price is gradually lower than the double-slope integrated analog-to-digital converter.
3. The digital rms circuit will have AC signal measurement parts regardless of voltage or current. In the past, measuring AC signal circuits differed in accuracy. There are several measurement methods in the AC measurement method classification table. From the analysis table of the AC measurement type classification table and the average response circuit measurement error of various waveforms, it can be known that the square root (so-called TrueRMS) is more accurate and important in AC signal measurement, but it must be added with a special component for RMS conversion. "RMS-DC (Root Mean Square-DC) Converter" is expensive and easy to ignore by the average user.
Although the rms conversion dedicated component can improve the measurement accuracy, the peak value of the voltage exceeding the crest factor will exceed the analog circuit input allowable range. The DMM dedicated chip described in this article has a high-precision, fast sigma-delta analog-to-digital converter that can implement digital RMS and Inrush Current measurement functions, and then use peak detection to achieve higher crest factor voltage measurements.
AC Measure Mode Classification Table Average Response Circuit Measures Various Waveform Errors (from Analog Devices.)
4.Low Pass Filter
In some mechatronic applications, there may be surges or other high-frequency signals entrained in the signal to be measured, and a low-pass filter (LowPass Filter) will be used to filter out high-frequency signals. The DMM dedicated chip introduced in this paper is to change the OSR (Over-Sampling Ratio) of the analog digital signal converter, and to achieve signal low-pass filtering, the same effect of high-frequency signal filtering, so that the value is more correct.
Low-pass filter (from Fluke289UsersManual)
LowPassActiveFilterfor10k Hzcutoff (from National Semiconductor ApplicationNote31)
5.PeakHold
In some electromechanical applications where peak values ​​need to be measured, the Peak Hold circuit is used to lock the voltage. Analog-to-digital converters perform voltage conversion. However, the capacitance of the circuit that locks the voltage is easily affected by the external environment. Something changed. The DMM dedicated chip introduced in this article has a digital peak detection and compares the analog to digital conversion results to make the value more accurate.
Low Drift Peak Detector (from National Semiconductor Application Note31)
6. Temperature Sensors Portable power measuring equipment, sometimes in addition to the measurement of electrical energy and components, increase the temperature measurement. There are four most common temperature sensors: Thermocouple, Resistance Temperature Detectors (RTD), Thermistors, and Integrated Circuits. In the portable power measurement device, the thermocouple measurement structure is often used, and the principle is that the voltage of the Seebeck effect is generated when the two metals are connected, but the voltage is zero when the temperature to be measured is the same as the ambient temperature. Do cold temperature compensation (Cold-Junction Compensation). The DMM dedicated chip described in this article has a temperature sensor.
Temperature Measurement Circuit. (From Texas Instruments OPAx235 Datasheet)
7. The standard serial interface HY12P65 has a UART (Universal Asynchronous Receiver/Transmitter) and SPI (Serial Peripheral Interface) interface. The new generation of portable digital instruments, most of which have UART interface and computer communication functions, can achieve automatic testing and product automatic correction. Reduce manual operating costs. The product calibration value or measurement value can be stored in the external memory (EEPROM or FLASH) of the MCU through the SPI interface.
8. OTPMCU
In addition to the DMM-specific analog front-end line, the HY12P65 integrates an 8-bit reduced instruction set (RISC) MCU that is suitable for low-to-medium-scale digital meters, which saves product circuit layout space and enables the product volume to be smaller.
Fourth, reference data:
lHY12P65(DMMSpecializedICEd DigitalT-RMS) Datasheet
lHY12P(Digital Multimeter)FamilyUser's Guide
lMakeBetterRMSMeasurementswithYourDMM,AgilentApplicationNote1392
lOpAmpCircuitCollection,NationalSemiconductorApplicationNote31
Fifth, chip manufacturers:
l Hycon Technology focuses on the measurement and monitoring of analog signals such as temperature, pressure, weight, voltage, current, and power. It mainly provides related chip development in battery management, instrumentation (including medical, measurement, temperature...), and industrial control.
I. Introduction:
Electronic motor personnel will use pointers and meters or Digital Multiple Meters (DMMs) during maintenance or experimentation. The past portable digital instrument industry used Harris (has been acquired by Intersil), JRC, and Maxim. Analog to Digital Converters (ADCs), which are manufactured by foreign manufacturers such as Samsung and Telcom (acquired by Microchip), convert input analog signals to digital signals for processing. However, the portable digital instrument industry is characterized by a small quantity, many types, and a long product life cycle. Therefore, these foreign integrated circuit manufacturers have no longer designed new A/D converters for digital multiplexed meters, and have even withdrawn from the market for A/D converters dedicated to digital multiplexed meters. The digital multiplex table requires only one chip plus resistors, capacitors, protection components, etc., to complete a product, so the threshold is not high, and the industry pie is so large that the end is the price war, and the profit is not as good as consumption. Sex products. For the digital multiplex table, the dedicated analog-to-digital converter is the core. Most of the portable instrument industry is relatively small, unlike Fluke, which can open its own dedicated DMM chip.
In recent years, the development of integrated circuits has been booming. There are several DMM-specific chip suppliers. There are two architectures in the analog-to-digital converters. They are Sigma-Delta and Dual Slop. For the architecture. This article will introduce the DMM dedicated chip of the Hycon HY12P65 mixed-signal processor (Mixed-Signal Microconductor), which uses a sigma-delta analog-to-digital converter architecture.
Second, the evolution of portable power meter:
The earliest portable power meter was a three-point meter. This generation of instruments has a low unit price, but it has low accuracy, low resolution, little functionality, and no input protection.
Since the beginning of the development of integrated circuits, chip vendors have designed analog-to-digital converters, so there are Handheld Manual Range Digital Multimeters, which use ICL7106, ICL7108, TLC7135, and HI-7159A analog digital. The converter, in addition to the voltage, resistance, and current measurements of the pointer triple-use meter, adds capacitance, frequency, and temperature, and the DMM manufacturer adds input protection circuitry. However, almost all functions require external circuit switching. When using it, the manual gear must be used to select the gear, which is inconvenient to use.
In order to simplify the operation, chip suppliers have designed DMM-specific analog-to-digital converters. Therefore, there are handheld automatic range digital multiple meters, and such meters use TelcomTC818A, SamsungKAD7001, and JRCNJU9210 analog-to-digital converters. In general, all the functions of the DMM are designed in the chip, as long as the resistance and capacitance are added, and the manual selection of the gear is not required in use.
However, users have new requirements such as high accuracy, high resolution, connection to a computer, or special features. Therefore, the chip supplier designs a component for the DMM dedicated analog front end (such as Maxim's MAX133/MAX134), or combines the analog front end with an MCU (such as Epson's S1C62M20), and the chip meets new requirements with the MCU. However, in addition to voltage, resistance, and current measurements, the chips of such products require additional functional circuits, which is not ideal.
In order to achieve the above new requirements, Fukang Technology has introduced a new generation of DMM-specific chips, such as HY12P65, to solve these problems.
Third, the chip new trend function overview:
In the future, the trend of the portable digital instrument industry must be to have its own product function planning in order to no longer be a price war. For example, an intelligent electric meter must rely on a more flexible DMM special chip. The new trends can be divided into the following categories according to their functions:
1. Switch network can be planned in the past DMM special chip will be fixed for each function and file bit switch network, the advantage is easy to design, but flexible switching multi-function network, can not have its own product function planning. The DMM special chip introduced in this article has a switchable network. If the domestic portable digital instrument industry, there is more room for product design.
â–²HY12P65Analog Switch Network
2. High resolution Σ-Δ analog-to-digital converter The DMM dedicated chip produced by foreign manufacturers in the past, A / D converters are used double slope integration as the framework, this architecture analog-to-digital converter conversion speed is slow, and used The quality of the integral capacitor affects the stability and the error of the entire converter. Usually the integral capacitor needs to use good materials such as MPE or MPP, and it is not easy to achieve high resolution.
The Σ-Δ analog digital signal converter has been used in more and more industrial control and advanced instrumentation in recent years. Its greatest advantage is its small number of peripheral circuits, high conversion speed, high resolution and accuracy, and it is less susceptible to power systems. For 50/60Hz and all effects, the unit price is gradually lower than the double-slope integrated analog-to-digital converter.
3. The digital rms circuit will have AC signal measurement parts regardless of voltage or current. In the past, measuring AC signal circuits differed in accuracy. There are several measurement methods in the AC measurement method classification table. From the analysis table of the AC measurement type classification table and the average response circuit measurement error of various waveforms, it can be known that the square root (so-called TrueRMS) is more accurate and important in AC signal measurement, but it must be added with a special component for RMS conversion. "RMS-DC (Root Mean Square-DC) Converter" is expensive and easy to ignore by the average user.
Although the rms conversion dedicated component can improve the measurement accuracy, the peak value of the voltage exceeding the crest factor will exceed the analog circuit input allowable range. The DMM dedicated chip described in this article has a high-precision, fast sigma-delta analog-to-digital converter that can implement digital RMS and Inrush Current measurement functions, and then use peak detection to achieve higher crest factor voltage measurements.
AC Measure Mode Classification Table Average Response Circuit Measures Various Waveform Errors (from Analog Devices.)
4.Low Pass Filter
In some mechatronic applications, there may be surges or other high-frequency signals entrained in the signal to be measured, and a low-pass filter (LowPass Filter) will be used to filter out high-frequency signals. The DMM dedicated chip introduced in this paper is to change the OSR (Over-Sampling Ratio) of the analog digital signal converter, and to achieve signal low-pass filtering, the same effect of high-frequency signal filtering, so that the value is more correct.
Low-pass filter (from Fluke289UsersManual)
LowPassActiveFilterfor10k Hzcutoff (from National Semiconductor ApplicationNote31)
5.PeakHold
In some electromechanical applications where peak values ​​need to be measured, the Peak Hold circuit is used to lock the voltage. Analog-to-digital converters perform voltage conversion. However, the capacitance of the circuit that locks the voltage is easily affected by the external environment. Something changed. The DMM dedicated chip introduced in this article has a digital peak detection and compares the analog to digital conversion results to make the value more accurate.
Low Drift Peak Detector (from National Semiconductor Application Note31)
6. Temperature Sensors Portable power measuring equipment, sometimes in addition to the measurement of electrical energy and components, increase the temperature measurement. There are four most common temperature sensors: Thermocouple, Resistance Temperature Detectors (RTD), Thermistors, and Integrated Circuits. In the portable power measurement device, the thermocouple measurement structure is often used, and the principle is that the voltage of the Seebeck effect is generated when the two metals are connected, but the voltage is zero when the temperature to be measured is the same as the ambient temperature. Do cold temperature compensation (Cold-Junction Compensation). The DMM dedicated chip described in this article has a temperature sensor.
Temperature Measurement Circuit. (From Texas Instruments OPAx235 Datasheet)
7. The standard serial interface HY12P65 has a UART (Universal Asynchronous Receiver/Transmitter) and SPI (Serial Peripheral Interface) interface. The new generation of portable digital instruments, most of which have UART interface and computer communication functions, can achieve automatic testing and product automatic correction. Reduce manual operating costs. The product calibration value or measurement value can be stored in the external memory (EEPROM or FLASH) of the MCU through the SPI interface.
8. OTPMCU
In addition to the DMM-specific analog front-end line, the HY12P65 integrates an 8-bit reduced instruction set (RISC) MCU that is suitable for low-to-medium-scale digital meters, which saves product circuit layout space and enables the product volume to be smaller.
Fourth, reference data:
lHY12P65(DMMSpecializedICEd DigitalT-RMS) Datasheet
lHY12P(Digital Multimeter)FamilyUser's Guide
lMakeBetterRMSMeasurementswithYourDMM,AgilentApplicationNote1392
lOpAmpCircuitCollection,NationalSemiconductorApplicationNote31
Fifth, chip manufacturers:
l Hycon Technology focuses on the measurement and monitoring of analog signals such as temperature, pressure, weight, voltage, current, and power. It mainly provides related chip development in battery management, instrumentation (including medical, measurement, temperature...), and industrial control.
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