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university:tools:m1k:hw [08 Dec 2014 17:37]
Robin Getz add shortlinks
university:tools:m1k:hw [18 Jul 2019 20:43]
Doug Mercer [Voltage Measurement]
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 +====== ADALM1000 ======
 +
 ===== Introduction ===== ===== Introduction =====
 +
 +{{ :​university:​tools:​m1k:​adalm1000_angle_small.png?​direct&​150|}}
  
 The [[adi>​ADALM1000]] is a learning tool designed to make interacting with the world around you easier and more intuitive. Offering two analog channels, it allows you to source and measure waveforms in voltage or current, easily characterizing arbitrary systems in terms of voltage vs current, over time, and over frequency. To offer this functionality,​ it uses a number of building blocks to take the fixed supply and digital interface of USB and offer voltage and current operation from 0 to 5 Volts (V), from -200 to 200 milliamps (mA), with precision and accuracy better than 100µV, 100µA, and 10µS. The [[adi>​ADALM1000]] is a learning tool designed to make interacting with the world around you easier and more intuitive. Offering two analog channels, it allows you to source and measure waveforms in voltage or current, easily characterizing arbitrary systems in terms of voltage vs current, over time, and over frequency. To offer this functionality,​ it uses a number of building blocks to take the fixed supply and digital interface of USB and offer voltage and current operation from 0 to 5 Volts (V), from -200 to 200 milliamps (mA), with precision and accuracy better than 100µV, 100µA, and 10µS.
  
-==== USB ====+===== USB =====
  
 [[wp>​USB|Universal Serial Bus (USB)]] is a high complexity, high speed digital interface designed for PC peripherals,​ offering a number of default device types and communication schemes. While tremendously useful for the "last inches"​ of interface between a host PC and the M1K, the pieces of the M1K responsible for converting between analog values and digital words (analog-digital converters (ADC) and digital-analog converters (DAC)) use simpler, less robust communication schemes necessitating "​glue"​ between a computer and the analog systems for voltage/​current measurement and control. On the M1K, this glue is a microcontroller using a CPU designed by ARM (Cortex M3). [[wp>​USB|Universal Serial Bus (USB)]] is a high complexity, high speed digital interface designed for PC peripherals,​ offering a number of default device types and communication schemes. While tremendously useful for the "last inches"​ of interface between a host PC and the M1K, the pieces of the M1K responsible for converting between analog values and digital words (analog-digital converters (ADC) and digital-analog converters (DAC)) use simpler, less robust communication schemes necessitating "​glue"​ between a computer and the analog systems for voltage/​current measurement and control. On the M1K, this glue is a microcontroller using a CPU designed by ARM (Cortex M3).
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 The microcontroller is only one of the pieces sitting between the USB connector and the analog components used for the front-end interface. Besides mapping between digital protocols, there is one more big problem to solve before we can build the analog system: power. The microcontroller is only one of the pieces sitting between the USB connector and the analog components used for the front-end interface. Besides mapping between digital protocols, there is one more big problem to solve before we can build the analog system: power.
  
-=== Power ===+===== Power =====
  
 The USB specification (available from the [[http://​www.usb.org/​home|USB implementers forum]]) is a 600+ page document describing every aspect of the ideal operation of a USB2.0 device. It requires that attached devices consume less than 500mA from the provided voltage supply, which is allowed to range from as high as 5.25v to as low as 4.40v - a wide span clearly unacceptable for a precision tool! Additionally,​ the power available on USB ports can vary widely in terms of both electrical noise and electrical protection. An [[wp>​USB#​Power|out-of-spec device]] attached to the shared USB bus can throw tens or even hundreds of millivolts of noise onto the voltage supply. A poorly crafted computer may not handle overcurrent conditions on a USB bus with anything more than an immediate and complete power-off, or worse, permanently disabling a USB port. It would be unfortunate if using the M1k on an old computer degraded the accuracy of measurements and unacceptable if making mistakes during the normal operation of the device put the attached computer at risk of damage or lost data. To address these issues and provide protected, low noise voltage supplies to the analog frontend, a sophisticated supply chain as designed to ensure that regardless of input, the full 0-5v range is available at the output, and regardless of shorting or over volting the device, the host PC is not exposed to unacceptable risk. The USB specification (available from the [[http://​www.usb.org/​home|USB implementers forum]]) is a 600+ page document describing every aspect of the ideal operation of a USB2.0 device. It requires that attached devices consume less than 500mA from the provided voltage supply, which is allowed to range from as high as 5.25v to as low as 4.40v - a wide span clearly unacceptable for a precision tool! Additionally,​ the power available on USB ports can vary widely in terms of both electrical noise and electrical protection. An [[wp>​USB#​Power|out-of-spec device]] attached to the shared USB bus can throw tens or even hundreds of millivolts of noise onto the voltage supply. A poorly crafted computer may not handle overcurrent conditions on a USB bus with anything more than an immediate and complete power-off, or worse, permanently disabling a USB port. It would be unfortunate if using the M1k on an old computer degraded the accuracy of measurements and unacceptable if making mistakes during the normal operation of the device put the attached computer at risk of damage or lost data. To address these issues and provide protected, low noise voltage supplies to the analog frontend, a sophisticated supply chain as designed to ensure that regardless of input, the full 0-5v range is available at the output, and regardless of shorting or over volting the device, the host PC is not exposed to unacceptable risk.
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 Having generated the voltages required for the output stage, additional clean supplies are required for operating other aspects of the analog systems. The data converters (DAC and ADC) require that the analog output/​input voltages are less than or equal to the supply voltage, and both require a supply voltage less than 5.5v. As such, a 5.0v rail is generated using the [[adi>​ADP7118]] linear regulator from the 6.0v rail described above, offering a low noise, high precision voltage supply for the remainder of the mixed-signal components, afforementioned AD5663R digital-analog converter, the two AD7682 analog-digital converters, the AD8210 current-sense differential amplifier, and the ADG719 analog mode-switch. The even lower noise 5.0v supply is in turn used to power a precision voltage reference, the [[adi>​ADR381]],​ which is used in conjunction with a 510 ohm load resistor to provide a high precision, low noise 2.5v supply capable of sourcing and sinking the few milliamps of current required by the analog frontend. Having generated the voltages required for the output stage, additional clean supplies are required for operating other aspects of the analog systems. The data converters (DAC and ADC) require that the analog output/​input voltages are less than or equal to the supply voltage, and both require a supply voltage less than 5.5v. As such, a 5.0v rail is generated using the [[adi>​ADP7118]] linear regulator from the 6.0v rail described above, offering a low noise, high precision voltage supply for the remainder of the mixed-signal components, afforementioned AD5663R digital-analog converter, the two AD7682 analog-digital converters, the AD8210 current-sense differential amplifier, and the ADG719 analog mode-switch. The even lower noise 5.0v supply is in turn used to power a precision voltage reference, the [[adi>​ADR381]],​ which is used in conjunction with a 510 ohm load resistor to provide a high precision, low noise 2.5v supply capable of sourcing and sinking the few milliamps of current required by the analog frontend.
  
-=== Analog Overview ===+===== Analog Overview ​=====
  
 ==== Digital-Analog Conversion ==== ==== Digital-Analog Conversion ====
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 ==== Voltage Measurement ==== ==== Voltage Measurement ====
 +
 +See [[university:​tools:​m1k:​analog-inputs|this page]] covering the analog voltage inputs.
  
 ==== Current Measurement ==== ==== Current Measurement ====
university/tools/m1k/hw.txt · Last modified: 22 Feb 2021 12:00 by Mihai Ionut Suciu