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SDM-INT8 8-Channel Interval Timer
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Overview

The SDM-INT8 outputs timing data to a Campbell Scientific datalogger. The datalogger can process the timing data to calculate RPM, duty cycle, velocity, crank angle, etc.

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Benefits and Features

  • Allows individual programming for each of the eight channels
  • Includes an internal microprocessor that allows measurement independent of data logger's execution interval
  • Outputs period, pulse width, frequency, counts, or time intervals
  • Records results as execution interval averages, continuous averages, specified interval averages, or capture all events

Technical Description

The SDM-INT8 has eight channels that are individually programmed to record the timing of input voltage transitions (events). It uses this information to output:

  • Period (ms)
  • Frequency (kHz)
  • Elapsed time between events on adjacent channels
  • Number of counts measured on channel 2 between a “start” event on channel 1 and a “stop” event on any other channel
  • Elapsed time between events on channel 1 and any other channel
  • Pulse Counting (any channel can function as a pulse counter)

High Level Voltage Input Pulses Schematic

Low Level AC Voltage Input Schematic

SDM Operation

The data logger enables individual modules through an addressing scheme; up to 15 SDM-INT8s can be connected to one data logger. After a module is enabled, it operates independently of the data logger until additional commands are received or results are transmitted.

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Specifications

Operating Voltage 9.6 to 16 Vdc
Current Drain
  • 13 to 20 mA (active)
  • 400 µA (quiescent)
Maximum Timing Measurement 16.7 s
Resolution ±1 µs
Operating Temperature -25° to +50°C
Dimensions 0.3 x 12.7 x 2.5 cm (8 x 5 x 1 in.)
Weight 0.82 kg (1.8 lb)

High-Level Voltage Input Pulses

Minimum Pulse Width 2 µs
Maximum Frequency (32-bit values)
  • The maximum frequency specification for high-resolution (32-bit) values assumes all eight channels are used.
  • 5.1 kHz (averaging options)
  • 10 kHz (capturing all events)
Maximum Frequency (16-bit values)
  • The maximum frequency specifications for low-resolution (16-bit) values is for the execution interval averaging only.
  • If number of channels programmed is
    • 1 channel—42.5 kHz
    • 2 channels—17.5 kHz
    • 3 channels—11 kHz
    • 4 channels—8.6 kHz
    • 5 channels—5.2 kHz
    • 6 channels—4.8 kHz
    • 7 channels—4.5 kHz
    • 8 channels—4.28 kHz

Low-Level AC Voltage Input

AC Voltage
  • 20 mV RMS (min.) ac voltage
  • 20000 mV RMS (max.) ac voltage
Input Hysteresis 11 mV
Minimum Frequency 1 Hz
Maximum Frequency
  • 100 kHz (20 mV min. RMS)
  • 400 kHz (50 mV min. RMS)
  • 1000 kHz (150 mV min. RMS)
  • 4000 kHz (2.5 to 20 V min. RMS)

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Dataloggers

Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR216X (retired)
CR3000 SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR5000 (retired) SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR6
CR800 (retired)
CR850 (retired)
CR9000X (retired) SDMs connect to ports provided on the CR9032 CPU module.

Mounting Equipment

Product Compatible Note
ENC10/12
ENC12/14
ENC14/16
ENC16/18

Miscellaneous

Product Compatible Note
GRANITE 10
GRANITE 6
GRANITE 9

Additional Compatibility Information

Data Logger Considerations

Programming

The SDMINT8 instruction controls the SDM-INT8 operation in CRBasic. Instruction 101 controls the SDM-INT8 operation in Edlog.

Power Considerations

The SDM-INT8 draws 20 mA. In most applications, the data logger’s sealed rechargeable power supply can be used. The data logger’s alkaline power supply has sufficient capacity to operate the SDM-INT8 during short-term installations only.

Enclosure Considerations

The SDM-INT8 should be housed in an environmental enclosure. A bracket is shipped with the SDM-INT8 for mounting it to an enclosure backplate.

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