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Application Notes

• Download
  Interfacing the LTC1090/1/2 &mdash AN26 (A-R)
  PDF, 5.6 Mb, File published: Jan 23, 1988
  A collection of interface applications between various microprocessors/ controllers and the LTC1090 family of data acquisition systems. The note is divided into sections specific to each interface.
• Download
  Data Acquisition Circuit Collection &mdash AN62
  PDF, 349 Kb, File published: Oct 1, 1994
  This application note presents a wide variety of data acquisition circuits. The detailed circuit schematics cover 8-, 10-, and 12- bit ADC and DAC applications, serial and parallel digital interfaces, battery monitoring, temperature sensing, isolated interfaces, and connections to various popular microprocessors and microcontrollers. An appendix covers suggested voltage references.
  Extract from the document

  Application Note 62
  October 1994
  Data Acquisition Circuit Collection
  Kevin R. Hoskins
  INTRODUCTION
  This application note features 8-, 10-, and 12-bit data
  acquisition components in various circuit configurations.
  The circuits include battery monitoring, temperature sensing, isolated serial interfaces, and microprocessor and
  microcontroller serial and parallel interfaces. Also included are voltage reference circuits (Application Note 42
  contains more voltage reference circuits). Additional circuit information is located in the information
  references listed in the Circuit Index. Each information
  reference refers to either an application note (example:
  AN42 = Application Note 42), a data sheet (example:
  LTCВ®1292 DS = LTC1292 Data Sheet), or a design note
  (example: DN66 = Design Note 66).
  and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation. CIRCUIT INDEX
  FIGURE TITLE
  FIGURE NO.
  General Analog-to-Digital Application Circuits
  Two-Quadrant 150kHz Bandwidth Analog Multiplier . Figure 1 .
  Infinite Hold-Time Sample-and-Hold (tACQ = 240ns) . Figure 2 .
  Four-Quadrant 250kHz Bandwidth Analog Multiplier . Figure 3 .
  Demodulating a Signal Using Undersampling . Figure 4 . …

Design Notes

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  Data Acquisition Systems Communicate with Microprocessors Over 4 Wires &mdash DN1
  PDF, 75 Kb, File published: Aug 1, 1987
  Extract from the document

  Data Acquisition Systems Communicate with
  Microprocessors Over 4 Wires – Design Note 1
  As board space and semiconductor package pins
  become more valuable, serial data transfer methods
  between microprocessors (MPUs) and their peripherals
  become more and more attractive. Not only does this
  save lines in the transmission medium, but, because
  of the savings in package pins, more function can be
  packed into both the MPU and the peripheral. Users are
  increasingly able to take advantage of these savings
  as more MPU manufacturers develop serial ports for
  their products1-3. However, peripherals which are able
  to communicate with these MPUs must be available in
  order for users to take full advantage. Also, MPU serial
  formats are not standardized so not all peripherals can
  talk to all MPUs.
  The LTC1090 Family
  A new family of 10-bit data acquisition circuits has
  been developed to communicate over just 4 wires to the
  recently developed MPU synchronous serial formats as
  well as to MPUs which do not have serial ports. These
  circuits feature software configurable analog circuitry
  including analog multiplexers, sample and holds, bipolar …

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  Electrically Isolating Data Acquisition Systems &mdash DN10
  PDF, 73 Kb, File published: May 1, 1988
  Extract from the document

  Electrically Isolating Data Acquisition Systems
  Design Note 10
  Guy Hoover and William Rempfer
  Introduction
  In data acquisition systems it is often necessary to
  electrically isolate the measurement points from the
  system controller. Reasons for the electrical isolation
  include the following: to allow floating measurements
  at high voltages; for safety, to reduce the danger of
  electrical shock, as might occur in medical applications;
  and to eliminate ground loops between measurement
  points and the system controller which can cause errors.
  The data transmitted over the isolated lines can be
  either analog or digital. Analog signals have poor noise
  immunity and one isolator is required for each signal
  point. Traditionally, the highly noise immune, digitally
  encoded signals required many isolated lines for each
  channel. Now, with the LTCВ®1090 family of serial data
  acquisition systems, it is possible to transmit eight
  channels of data with only four isolated lines. Each
  additional eight channels requires only one additional
  isolated line.
  Both opto isolators and pulse transformers could be …

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  Closed Loop Control with Data Acquisition Systems &mdash DN13
  PDF, 95 Kb, File published: Aug 1, 1988
  Extract from the document

  Closed Loop Control with Data Acquisition Systems
  Design Note 13
  Guy Hoover and William Rempfer
  Introduction
  The use of microprocessors in process control loops
  is quite common. A processor based control loop requires special design considerations as compared to
  traditional analog loops. Often a single centrally located
  processor will be used to control several remotely
  located processes. The outputs of the remote process
  sensors can be digitized at the sensor location and then
  be transmitted to the central processor. Unfortunately,
  transmitting digital signals typically requires one wire
  for each bit of resolution and requires expensive cabling.
  Alternatively, the sensor output can be transmitted
  as an analog signal to the central processor area for
  digitization. However, transmitting analog signals over
  distances can introduce errors because of noise and
  voltage drops in the wires.
  The solution to these control loop problems can be found
  in the LTC В®1090 series of data acquisition systems. As
  can be seen in the schematic of Figure 2, ten bits of
  data can be digitized remotely and sent to the processor
  with only three wires plus ground. The single supply …

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  Sampling of Signals for Digital Filtering and Gated Measurements &mdash DN2
  PDF, 377 Kb, File published: Oct 1, 1987
  Extract from the document

  Sampling of Signals for Digital Filtering and
  Gated Measurements – Design Note 2
  William Rempfer
  Introduction
  For many signal processing applications a sample and
  hold function is required in a data acquisition system. It
  is often critical for the processing system to know the
  exact value of an analog input at an exact time. In DSP
  applications such as digital filters, the usable bandwidth
  of the system is limited by the Nyquist frequency and the
  sample and hold bandwidth need only be, and is often
  intentionally limited to, one half the sampling rate. However,
  another area of application requires infrequently capturing
  instantaneous values of relatively fast signals, sometimes
  referred to as gated measurements. In the extreme case
  of pulse height measurements, only one sample point is
  required. Here, the sample and hold bandwidth should
  be as high as possible even though the sampling rate is
  very low.
  The LTC В®1090 excels in both environments. This note
  shows how the LTC1090 sample and hold can be synchronized to an external event and gives two simple
  applications: an 8-channel data acquisition system with
  digital filtering, and the gated measurement of a 1MHz …

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  Auto-Zeroing A/D Offset Voltage &mdash DN26
  PDF, 83 Kb, File published: Sep 1, 1989
  Extract from the document

  Auto-Zeroing A/D Offset Voltage
  Design Note 26
  Guy Hoover and William Rempfer
  Introduction
  Many A/D converters exhibit low offset errors with large
  full scale voltages. However, when the full scale voltage
  is decreased the VOS, expressed in LSBs, increases. An
  A/D converter with 0.5 LSB of offset with a 5V full scale
  voltage can have 12.5 LSBs of offset with a 200mV
  full scale voltage. With the LTCВ®1090 family of data
  acquisition systems and a few external components
  it is now possible to reduce the VOS to only 0.25 LSB
  even with only a 200mV full scale voltage. This allows
  a user to digitize signals from low voltage transducers
  without the need for a gain stage. Circuit Description
  The LTC1090 is a 10-bit data acquisition system with
  an eight channel multiplexer. The channel to be read
  is software selectable and all channels can be referred
  to the COM pin. In the circuit of Figure 1, CH0 is used
  to servo the COM pin giving the use a seven channel,
  offset corrected data acquisition system.
  Figure 2 shows how the processor servos the COM
  pin to eliminate the A/D offset. CH0 is set to a 0.5 LSB …

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  12-Bit 8-Channel Data Acquisition System Interfaces to IBM PC Serial Port &mdash DN35
  PDF, 101 Kb, File published: Jun 1, 1990
  Extract from the document

  12-Bit 8-Channel Data Acquisition System Interfaces to IBM PC
  Serial Port – Design Note 35
  Guy Hoover and William Rempfer
  IBM PCs Collect Analog Data
  IBM PC compatibles can be found just about everywhere.
  In those instances where a PC is not already in place,
  battery operated portables are readily available. This
  makes the PC a good choice for controlling a data acquisition system. Typically, such data acquisition systems
  have been expensive. Using dedicated A/D cards or
  IEEE-488 controllers and instruments, these systems
  tie up slots in the PC and are not readily transportable
  from one machine to another. As an alternative, the
  schematic of Figure 1 shows a 12-bit, 8-channel data
  acquisition system that connects to the serial port of
  the PC. This system uses an LTC В®1290, a reference,
  a handful of other low cost components and requires
  12 lines of BASIC to transfer data into the PC. If only
  ten bits of resolution are required the LTC1290 can be
  replaced with an LTC1090. Additionally, if the LTC1090
  is used, the system can be powered directly from the
  PC serial port with the option shown. Two Glue Chips Provide the Interface
  The control and status lines of the PC serial port are
  used to send data to and receive data from the LTC1290. …

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  Temperature Measurement Using Data Acquisition Systems &mdash DN5
  PDF, 77 Kb, File published: Mar 1, 1989
  Extract from the document

  Temperature Measurement Using Data Acquisition Systems
  Design Note 5
  William Rempfer and Guy Hoover
  Introduction
  Accurate temperature measurement is a difficult and
  very common problem. Whether recording a temperature, regulating a temperature or modifying a process
  to accommodate a temperature, the LTCВ®1090 family
  of data acquisition systems can provide an important
  link in the chain between the blast furnace temperature
  and the microcontroller. Features of the LTC1090 family
  can make temperature measurement easier, cheaper
  and more accurate.
  High DC input resistance and reduced span operation
  allow direct connection to many standard temperature
  sensors. Multiplexer options allow one chip to measure
  up to 8 channels of temperature information. Single
  supply operation, modest power requirements (~5mW)
  and serial interfaces make remote location possible.
  Switching power on and off lowers power consumption (560ОјW) even more for battery applications.
  Finally, because few sensors have accuracies as good as 0.1%, the 10-bit resolution and 0.05% accuracy of
  the LTC1090 family are just right for most temperature
  sensing applications.
  Thermocouple Systems …

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Manufacturer's Classification

• Data Conversion > Analog-to-Digital Converters (ADC) > Precision ADCs (Fs < 10Msps) > Multi Channel ADCs