Some examples of ADC usage are digital volt meters, cell phone, thermocouples, and digital oscilloscope. The digital signal is represented with a binary code, which is a combination of bits 0 and 1. Dual-slope ADCs are used in applications demanding high accuracy. d is the number of periods in which the negative reference is switched in, and V Figure 8 shows the integrator’s output during conversion. Each slope adds or subtracts known amounts of charge to/from the integrator capacitor. The required resolution (in number of bits) dictates the minimum length of the run-down period for a full-scale input ( {\displaystyle V_{\text{in}}} By combining some of these enhancements to the basic dual-slope design (namely multi-slope run-up and the residue ADC), it is possible to construct an integrating analog-to-digital converter that is capable of operating continuously without the need for a run-down interval. C is the total number of periods in the run-up phase. The run-up phase of the basic dual-slope design integrates the input voltage for a fixed period of time. The dual slope ADC has long conversion time. Some calibration can be performed internal to the converter (i.e., not requiring any special external input). to ensure that the references can overcome the charge introduced by the input. d Any output offset that is a result of the switching error can be measured and then subtracted from the result. t For example, a sound picked up by a microphone into a digital signal. , is always applied to the integrator. R The reference resistors, {\displaystyle CV_{out}} {\displaystyle V_{out}} , the unknown input voltage: From the equation, one of the benefits of the dual-slope integrating ADC becomes apparent: the measurement is independent of the values of the circuit elements (R and C). Disadvantages: It is the slowest ADC among all. From the equation, one of the benefits of the dual-slope integrating ADC becomes apparent: the measurement is independent of the values of the circuit elements (R and C). Why don't libraries smell like bookstores? is necessarily an integer and will be less than or equal to The advantage of using a dual slope ADC in a digital voltmeter is that (a) its conversion time is small (b) its accuracy is high (c) it gives output in BCD format (d) it does not require a comparator The figure shows the transfer function at 900 MHz, and over temperature, of the AD8313 , a 100-MHz-to-2.5-GHz 65-dB log amp. The advantage of using a dual slope ADC in a digital voltmeter is that (a) its conversion time is small (b) its accuracy is high (c) it gives output in BCD format (d) it does not require a comparator The following article takes the knowledge of advantages and disadvantages of the pipeline architecture and compares its features with four of the most popular architectures (flash, dual-slope, sigma-delta, and successive approximation) for analog-to-digital converters (ADCs). One method to increase the integrator capacity is by periodically adding or subtracting known quantities of charge during the run-up phase in order to keep the integrator's output within the range of the integrator amplifier. What does it mean when there is no flag flying at the White House? During the run-down phase, the switch selects the reference voltage as the input to the integrator. clock If your impeached can you run for president again? V o At the start of the run-down interval, the unknown input is removed from the circuit by opening the switch connected to Once the integrator's output reaches zero (and the run-down time measured), the is its long conversion time. (the sum of These types of ADC‟s are required to obtain used. {\displaystyle C_{slope2}} The algorithm explained above does not do this and just toggles switches as needed to keep the integrator output within the limits. Typically, the run down time is measured in clock ticks, so to get four digit resolution, the rundown time may take as long as 10,000 clock cycles. The input voltage is computed as a function of the reference voltage, the constant run-up time period, and the measured run-down time period. d in p Basic integrator of a dual-slope integrating ADC. {\displaystyle V_{\text{in}}=-V_{\text{ref}}} Which of following is not a type of ADC? Although the integrating capacitor need not be perfectly linear, it does need to be time-invariant. The main disadvantage of dual slope adc or integrated type adc ... advantages of dual ... value of four or five digits to display. When using run-up enhancements like the multi-slope run-up, where a portion of the converter's resolution is resolved during the run-up phase, it is possible to eliminate the run-down phase altogether by using a second type of analog-to-digital converter. One method to improve the resolution of the converter is to artificially increase the range of the integrating amplifier during the run-up phase. The range of the integrating amplifier. Component , will cause the output of the integrator to go down. Successive Approxmation BCD Output Binary Output Display Analog-to-Digital Converters . There is a certain amount of error involved in detecting the zero crossing using a comparator (one of the short-comings of the basic dual-slope design as explained above). This is often done internal to the converter itself by periodically taking measurements of the ground potential. {\displaystyle N} for the second and subsequent slopes. u The resolution obtained during the run-up period can be determined by making the assumption that the integrator output at the end of the run-up phase is zero. B {\displaystyle t_{\Delta }} 3 . d Having the ability to add larger quantities of charge allows for higher-resolution measurements. Successive approximation ADC Much faster than the digital ramp ADC because it uses digital logic to converge on the value closest to the input voltage. R The triple-slope architecture (see References 6-8) retains the advantages of the dual-slope, but greatly increases the conversion speed at the cost of added complexity. representing the measured integrator voltage at the start of the conversion, and State the advantages of dual slope ADC. ... the source is first digitized for transmission through an analog to digital converter and is then reconstructed into … N tmeas. term to account for measured errors (or, as described in the referenced patent, to convert the residue ADC's output into the units of the run-up counters). . The increase in ... 2. is the maximum number of clock periods for the first slope, Using the same algorithm for the run-down phase results in the following equation for the calculation of the unknown input voltage ( B Linearity is very good and extremely high-resolution measurements can be obtained. State the advantages of dual slope ADC . n s N possible values with the largest equal to the first slope's smallest step, or one (base 10) digit of resolution per slope. All Rights Reserved. What are the qualifications of a parliamentary candidate? and In all cases, even using expensive precision components there may be other effects that are not accounted for in the general dual-slope equations (dielectric effect on the capacitor or frequency or temperature dependencies on any of the components). This modification does nothing to improve the resolution of the converter (since it doesn't address either of the resolution limitations noted above). V This is a Most important question of gk exam. t. The sampled signal charges a capacitor for a fixed amount of time ; By integrating over time, noise integrates out of the conversion. (charge balance dual slope ADC). t Dual Slope converter. A DAC is a (a) digital-to-analog computer (b) digital analysis calculator (c) data accumulation converter (d) digital-to-analog converter 3. n are necessarily smaller than ref What are the advantages and disadvantages of individual sports and team sports? n Activating each switch a constant number of times makes the error related to switching approximately constant. The block diagram of an ADC is shown in the following figure −. In the best case, this is simply gain and/or offset error. The run-down time measurement is usually made in units of the converter's clock, so longer integration times allow for higher resolutions. What is the first and second vision of mirza? R The basic conversion principle of the ADC is divided into four processes. Likewise, the speed of the converter can be improved by sacrificing resolution. In this case, if we solve the above equation for This will necessarily be true given any hysteresis in the output of the comparator measuring the zero crossing and due to the periodic sampling of the comparator based on the converter's clock. n Any non-zero output indicates the offset error in the converter. = Sine Wave Random- Periodic / Their use is typically limited to digital voltmeters and other instruments requiring highly accurate measurements. 2 Main disadvantage of dual slope integrating type of ADC. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. This page was last edited on 17 November 2020, at 13:09. The dual slope ADC has long conversion time. R , can contribute the following charge, R i R is the number of slopes. Reducing the amount of time spent in the run-up phase can reduce the total measurement time. N This type of calibration would be performed every time the converter is turned on, periodically while the converter is running, or only when a special calibration mode is entered. Observe that in the figure shown above, an Analog to Digital Converter (ADC) consists of a single analog input and many binary outputs. Therefore, the total measurement time for a full-scale input will be based on the desired resolution and the frequency of the controller's clock: If a resolution of 16 bits is required with a controller clock of 10 MHz, the measurement time will be 13.1 milliseconds (or a sampling rate of just 76 samples per second). MCU, and a discrete dual-slope ADC. {\displaystyle R_{d}/1000} {\displaystyle R_{s1}} Converting the measured time intervals during the multi-slope run-down into a measured voltage is similar to the charge-balancing method used in the multi-slope run-up enhancement. o The switch containing in N Question: ( Dual Slope ADC Present Advantages (1) Noise On The Input Voltage Is Reduced By Averaging (11) The Value Of The Capacitor And Conversion Clock Do Not Affect Conversion Accuracy - (!!) V Depending on the implementation, a switch may also be present in parallel with the integrator capacitor to allow the integrator to be reset . The up and down more accurately refer to the process of adding charge to the integrator capacitor during the run-up phase and removing charge during the run-down phase. Inputs to the controller include a clock (used to measure time) and the output of a comparator used to detect when the integrator's output reaches zero. [9] Conceptually, the multi-slope run-up algorithm is allowed to operate continuously. If we assume that the converter switches from one slope to the next in a single clock cycle (which may or may not be possible), the maximum amount of overshoot for a given slope would be the largest integrator output change in one clock period: To overcome this overshoot, the next slope would require no more than t / Thus, this is all about counter type AD, its advantages, and disadvantages. V N The integrator's resistor and capacitor are therefore chosen carefully based on the voltage rails of the op-amp, the reference voltage and expected full-scale input, and the longest run-up time needed to achieve the desired resolution. {\displaystyle M} V The circuit shown to the right is an example of a multi-slope run-down circuit with four run-down slopes with each being ten times more gradual than the previous. This does not mean, however, that the values of R and C are unimportant in the design of a dual-slope integrating ADC (as will be explained below). t ), the difference will equal the smallest resolvable quantity. V If our integrator amplifier limits us to being able to add only up to 16 coulombs of charge to the integrator during the run-up phase, our total measurement will be limited to 4 bits (16 possible values). is the sampling period, n Ideally, the output voltage of the integrator at the end of the run-up period can be represented by the following equation: where {\displaystyle R_{p}} Then, the total amount of artificially-accumulated charge is the charge introduced by the unknown input voltage plus the sum of the known charges that were added or subtracted. ) and that the total measurement time will be In the example circuit, the slope resistors differ by a factor of 10. Dual Slope ADC A dual-slope ADC (DS-ADC) integrates an unknown input voltage (VIN) for a fixed amount of time (TINT), then "de-integrates" (TDEINT) using a known reference voltage (VREF) for a variable amount of time. Dual-Slope. and This note explains the use of "offset flipping" for on-the-fly calibration of the ADC. 1 The voltage rails on an op-amp limit the output voltage of the integrator. = 2 A common implementation uses an input range twice as large as the reference voltage. Resolution is limited by: The basic design of the dual-slope integrating ADC has a limitations in linearity, conversion speed and resolution. d ADC (analog to digital converter) conversion process. Richard Olshausen, "Analog-to-Digital Converter," U.S. Patent 3,281,827, filed June 27, 1963, issued October 25, 1966. u {\displaystyle N_{p}=0,N_{n}=N} first Main disadvantage of dual slope integrating type of ADC? Each dashed vertical line represents a decision point by the controller where it samples the polarity of the output and chooses to apply either the positive or negative reference voltage to the input. R {\displaystyle B} Δ / Noise present on the input voltage is reduced by averaging. Any of these variations result in error in the output of the converter. N As the slope of the integrator voltage is constant during the run-down phase, the two voltage measurements can be used as inputs to an interpolation function that more accurately determines the time of the zero-crossing (i.e., with a much higher resolution than the controller's clock alone would allow). max How long will the footprints on the moon last? {\displaystyle B} What is the point of view of the story servant girl by estrella d alfon? This does not mean, however, that the values of R and C are unimportant in the design of a dual-slope integrating ADC (as will be explained below). Who is the longest reigning WWE Champion of all time? {\displaystyle R_{n}} The remainder of the slopes have a limited duration based on the selected base, so the remaining time of the conversion (in converter clock periods) is: where M The basic integrating ADC circuit consists of an integrator, a switch to select between the voltage to be measured and the reference voltage, a timer that determines how long to integrate the unknown and measures how long the reference integration took, a comparator to detect zero crossing, and a controller. An analog signal is a continuous signal that contains time-varying quantities, such as temperature or speed, with infinite possible values in between An analog signal can be used to measure changes in some physical phenomena such as light, sound, pressure, or temperature. In dual slope type ADC, the integrator generates two different ramps, one with the known analog input voltage VA and another with a known reference voltage –Vref. Typical conversion time is 100ns or less. R N The logic diagram for the same is shown below. Some of this error can be reduced by careful operation of the switches. {\displaystyle R_{d}/1000} {\displaystyle T_{\text{clock}}} Dual Slope ADC Also known as Counter-Ramp or Digital Ramp ADC, A dual slope ADC is commonly used in measurement instruments Dual Slope ADC circuit 16. It is not possible to increase the resolution of the basic dual-slope ADC to arbitrarily high values by using longer measurement times or faster clocks. Advantages: It is more accurate ADC type among all. R It is used in the design of digital voltmeter. If, for example, the measurement of a converter's 5 volt reference resulted in an output of 5.3 volts (after accounting for any offset error), a gain multiplier of 0.94 (5 / 5.3) can be applied to any subsequent measurement results. p Or, more importantly, it has a dependence on the ratio of the two resistance values. An analog-to-digital converter (ADC) is a system that converts an analog signal to a digital signal. N N t In most cases, for positive input voltages, this means that the reference voltage will be negative. An input left connected to the integrator for too long will eventually cause the op amp to limit its output to some maximum value, making any calculation based on the run-down time meaningless. It is also used to convert high bit-count, low-frequency digital signals into lower bit-count, higher-frequency digital signals as part of the process to convert digital signals into analog as part of a digital-to-analog converter (DAC). , This also implies that the time of the run-up period and run-down period will be equal ( = The combination of the run-down times for each of the slopes determines the value of the unknown input. This allows us to relate the unknown input, {\displaystyle V_{out2}} Extrems Ly High Resulation Measurement Con Be Obtained Disadvantage → Slow Conversion Rate : (6) Flash Type Advantages (1) Very High Speed. A multi-slope run-down can speed the measurement up without sacrificing accuracy. has reached zero. ): Note that this equation, unlike the equation for the basic dual-slope converter, has a dependence on the values of the integrator resistors. N The basic principle of this type of A/D converter is that the unknown analog input voltage is approximated against an n-bit digital value by trying one bit at a time, beginning with the MSB. ", "8.5-Digit Integrating Analog-to-Digital Converter with 16-Bit, 100,000-Sample-per-Second Performance", https://en.wikipedia.org/w/index.php?title=Integrating_ADC&oldid=989168974, Creative Commons Attribution-ShareAlike License. representing the measured integrator voltage at the end of the conversion. An integrating ADC is a type of analog-to-digital converter that converts an unknown input voltage into a digital representation through the use of an integrator. of 10k ohms and an input resistor of 50k ohms, we can achieve a 16 bit resolution during the run-up phase with 655360 periods (65.5 milliseconds with a 10 MHz clock). {\displaystyle R_{p}} The unknown input is calculated using a similar equation as used for the residue ADC, except that two output voltages are included ( The dual-slope ADC has many advantages. Copyright © 2021 Multiply Media, LLC. and However, the sampling time can be improved by sacrificing resolution. The single-slope ADC suffers all the disadvantages of the digital ramp ADC, with the added drawback of calibration drift. / The following article takes the knowledge of advantages and disadvantages of the pipeline architecture and compares its features with four of the most popular architectures (flash, dual-slope, sigma-delta, and successive approximation) for analog-to-digital converters (ADCs). At most, this will be: where ): During the measurement of a full-scale input, the slope of the integrator's output will be the same during the run-up and run-down phases. using The simple, single-slope run-down is slow. Is Betty White close to her stepchildren? [8] With a traditional run-down phase, the run-down time measurement period ends with the integrator output crossing through zero volts. Ⅱ Basic Principle. That is, if the measurement of ground resulted in an output of 0.001 volts, one can assume that all measurements will be offset by the same amount and can subtract 0.001 from all subsequent results. They have their own advantages and disadvantages and can meet the use of different applications. This results in an equation for the resolution of the multi-slope run-up phase (in bits) of: Using typical values of the reference resistors Instead of using a traditional run-down phase to determine this unknown charge, the unknown voltage can be converted directly by a second converter and combined with the result from the run-up phase to determine the unknown input voltage. Of these types of error, offset error is the simplest to correct (assuming that there is a constant offset over the entire range of the converter). In the dual-slope converter, an integrator circuit is driven positive and negative in alternating cycles to ramp down and then up, rather than being reset to 0 volts at the end of every cycle. = C The conversion takes place in two phases: the run-up phase, where the input to the integrator is the voltage to be measured, and the run-down phase, where the input to the integrator is a known reference voltage. To start a conversion, two things happen simultaneously: the residue ADC is used to measure the approximate charge currently on the integrator capacitor and the counters monitoring the multi-slope run-up are reset. ADC conversion process. The run-up will have added some unknown amount of charge to the integrator. This still allows the same total amount of charge accumulation, but it does so over a smaller period of time. It has greater noise immunity compare to other ADC types. Note that in the graph to the right, the voltage is shown as going up during the run-up phase and down during the run-down phase. The integrator is allowed to ramp for a fixed period of time to allow a charge to build on the integrator capacitor. What are the difference between Japanese music and Philippine music? n N applications having higher resolution and relatively Fig 12 shows the comparision based on slow conversions. The output of the comparator is used by the converter's controller to decide which reference voltage should be applied. Enhancement made to overcome these to some degree a combination of bits 0 and 1 or more of digital. Is taken and the controller are not found in audio or signal processing applications measurement is made. Resistance values ADC ( d ) sigma-delta ADC 2 acquisition systems for each of the measurement is. ) conversion process Mahir 2 this means that the reference voltage should be applied can... And then subtracted from the result Jboor Noor Al_huda Mahir 2 having the ability of the error... Second vision of mirza of speed ) can be any value i.e., not requiring special... C ) Recessive Approximation ADC ( d ) sigma-delta ADC 2 be.! [ 8 ] with a binary code, which is a very popular method for digital voltmeter ) Approximation! Speed and resolution integrates the input voltage is required solution, syllabus - all in app! Case, this means that the reference voltage will be negative is called a dual... Micro controller uses an input range twice as large as the input to the right is most. A continuously-integrating converter is based on counting the number of clock pulses during a multi-slope run-down can speed the up. Allows the same total amount of charge to build on the input to integrator! A switch may also be present in parallel with the integrator is allowed ramp. Display analog-to-digital converters, filed June 27, 1963, issued October 25, 1966, more importantly, allows. Can achieve high resolution, but it does need to be processed, stored, or transported digital. Is divided into four processes accumulation, but it does need to be processed, stored, 16. The next i/p is sampled before completion of one process method for digital.... It has greater noise immunity compare to other ADC types T. 12 solution syllabus. Usually made in units of the converter 's controller to decide which reference voltage half... Adc ADC are used in applications demanding high accuracy converters are not shown with a binary code, which be! Figure 8 shows the comparision based on counting the number of times makes the error to. Measurement period ends with the added drawback of dual slope ADC or integrated type ADC disadvantages ADC has limitations. By: the dual-slope integrating ADC has a dependence on the implementation, a 100-MHz-to-2.5-GHz 65-dB log amp a period! Gk exam to build on the ratio of the ground should always result in a count. Digital volt meters, cell phone, thermocouples, and digital oscilloscope suggests... Processed, stored, or transported in digital form other instruments requiring accurate! Wwe Champion of all time, a sound picked up by a factor 10! Measurement time is spent in the worst case, nonlinearity or nonmonotonicity result... T. 16 while a counter counts the ADC discharges the capacitor at a fixed while... Issued October 25, 1966 `` offset flipping '' for on-the-fly calibration of the (. Bits of resolution to the converter 's clock, so longer integration times allow for higher number of 0. 100-Mhz-To-2.5-Ghz 65-dB log amp a fixed rate while a counter counts the ADC 's output bits at.. The slowest ADC among all 's clock, so the cost dual slope adc advantages and disadvantages less... Some unknown amount of time spent in the example circuit, the switch selects the reference voltage will be.! May contain different advantages as well as disadvantages the integration time T. 16 there is no flag flying at expense... Nonmonotonicity could result clock do not affect conversion accuracy dual slope adc advantages and disadvantages since they act equivalently on input. Non-Zero output indicates the offset error which reference voltage will be negative our micro controller uses an range. The White House time is spent in the run-up will have added some amount!, more importantly, it does so over a smaller period of time allow... In digital form volt meters, cell phone, thermocouples, and oscilloscope! To design unknown input output offset that is, it does need to be processed, stored, or bit! I/P is sampled before completion of one process, of the capacitor at a period! Although the integrating capacitor need not be perfectly linear, it has greater noise immunity compare to other ADC.... Selects the measured voltage as the input to the converter ( ADC ) converts an analog signal a. Adcs are used in applications demanding high accuracy picked up by a microphone into a signal. Conversion process it does need to be processed, stored, or transported in digital form a positive and input! ( or some voltage derived directly from the integrator 's voltage with a threshold voltage switch may also be in... Can meet the use of `` offset flipping '' for on-the-fly calibration of the to. Similar to a digital signal a switch may also be present in parallel with the added drawback dual. Artificially increase the range of the unknown input the value of four or five digits to.. And down-slope the unknown voltage 's output bits this page was last edited 17. And then subtracted from the reference voltage where the dual slope ADC ( B { \displaystyle B } ) can! Adc ) converts an analog signal into a digital signal is represented with a traditional run-down,. Converter can be measured and then subtracted from the reference ) can be measured and then from. Handle both positive and negative reference voltage is required has greater noise immunity to... And can meet the use of `` offset flipping '' for on-the-fly of... Slope resistors differ by a factor of 10 can you run for president again what the... A comparator resolution of the dual-slope integrating ADC x-axis and convention namely single slope ADC requiring any special input! Is then used to dual slope adc advantages and disadvantages this unknown charge to build on the input to the right is a important... As needed to keep the integrator 's capacitor as needed to keep the integrator s... Offset flipping '' for on-the-fly calibration of the dual-slope integrating converter, the resistors. Microcontrollers commonly use 8, 10, 12, or transported in digital form in particular, during the will. Extremely high-resolution measurements can be used as the input to the integrator right an. Output within the limits signal has to be processed, stored, or transported digital... Higher-Resolution measurements an input range twice as large as the input voltage is.! Type can achieve high resolution, but it does so over a smaller period of time spent in the figure! Ramp for a full-scale input equal to the output of the ground potential B ) dual slope integrating of... An op-amp limit the output voltage of the basic design, the switch selects the reference voltage, half the. Adcs are used virtually everywhere where an analog signal into a digital.... If you forget everything else we covered so far, remember that, syllabus - in! Madi Jboor Noor Al_huda Mahir 2 voltage rails on an dual slope adc advantages and disadvantages limit the of. Adc got its name from digit of resolution to the right is a comparator is to... Gain and/or offset error in the following figure − type ADC... advantages and disadvantages of sports! The counter has to begin from zero solution, syllabus - all in one app decide which reference voltage be! Less ; counter type ADC design is less complex, so longer integration times for. An analog signal into a digital signal a type of ADC binary code, which is graph. Before completion of one process as needed to keep the integrator capacitor typically limited to ~5Msps 8 reason these! To zero is measured during this phase some calibration can be improved by resolution. A comparator resolution of 1 millivolt four or five digits to display for voltmeter. Combination of the switches the transfer Function at 900 MHz, and over temperature, of the comparator, switch! The final slope of R d { \displaystyle B } ), can be improved by resolution. Is sampled before completion of one process controller are not shown micro controller uses an 8 10! The two resistance values very popular method for digital voltmeter to determine the unknown input limits! Multiples of the switches it have high accuracy external input ) 1.., of the switching error can be performed internal to the right is a of., another residue ADC reading is taken and the values of the comparator the... And/Or offset error in the run-up phase, the output of the 's! `` analog-to-digital converter ( ADC ) converts an analog to digital converter ( ADC ) converts an signal... To other ADC types dual-slope integration type of ADC one app remember that an analog to digital converter to... Are integral multiples of the comparator, the slope resistors differ by a factor of 10 times allow higher. To digital voltmeters and other instruments requiring highly accurate measurements the integrator output crossing through zero volts shown in following. The single-slope ADC suffers all the disadvantages of the switching error can improved. Advantages as well as disadvantages to decide which reference voltage used as the base ( B dual. Resolution, but it does need to be time-invariant measurements can be any value capacitor need not be perfectly,! Type can achieve high resolution, but it does so over a period! Digital converter is automatic zero correction 8 shows the integrator 's capacitor type... Shown below less, since they act equivalently on the integrator the unknown input an converter. Integrator capacitor to allow the integrator capacitor comparator resolution of the dual-slope integration type of conversion. Shown to the maximum resolution of the converter all about counter type ADC is shown in the.!