Campbell Scientific SDM-INT8 User Manual

SDM-INT8

8 Channel Interval Timer

Revision: 12/11

Copyright © 1989-2011

Campbell Scientific, Inc.

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SDM-INT8 Table of Contents

PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.

1. Overview.......................................................................2

2. Specifications ..............................................................3

3. Connections ................................................................. 4

4. Power Supply Considerations....................................5

5. Programming the Datalogger .....................................5

5.1 CRBasic Programming .............................................................................6

5.1.1 Instruction SDMINT8.....................................................................6

5.1.2 SDMSpeed Instruction....................................................................8

5.2 Edlog Programming (Instruction “101”) ..................................................9

6. Programming Details.................................................10

6.1 Parameter 1 - Address.............................................................................10

6.2 Input Configuration ................................................................................11

6.3 Parameters 4 and 5 - Functions...............................................................11

6.4 Output Option .........................................................................................13

6.4.1 Rules for Averaging......................................................................13

6.4.2 Option 0: Execution Interval Averaging......................................16

6.4.3 Option 32768 or 0--: Continuous Averaging ................................16

6.4.4 Option nnnn or XXXX: Specified Averaging Interval ................17

6.4.5 Option –nnnn or XXXX--: Capture All Events Until nnnn

or XXXX Edges On Channel 1.................................................17

6.4.5.1 Option –nnnn.......................................................................17

6.4.5.2 Option XXXX-- ..................................................................17

6.4.6 Option 9999--: Test Memory .......................................................18

6.5 Dest, Input Location, Multiplier, and Offset ..........................................19

6.6 Edlog Output Format ..............................................................................19

7. Program Examples ....................................................20

7.1 CRBasic Program Example ....................................................................20

7.2 Edlog Program Examples .......................................................................21

7.2.1 Cold Crank Engine Test - Capture All Events..............................21

7.2.2 Wind Speed Measurements - Execution Interval Averaging........23

7.2.3 Brake Pressure and Wheel Speed Test - Capture All Events

and P23 Burst Mode..................................................................24

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SDM-INT8 Table of Contents

Appendices

A. Address Jumper ...................................................... A-1

B. Processing Time Limitations ................................. B-1

C. INT8 Input Schematic..............................................C-1

List of Figures

List of Tables

1. SDM-INT8 Front Panel ............................................................................. 1

2. Voltage Input Options, Edges and Thresholds........................................... 2

3. Wiring Diagram ......................................................................................... 5

4. Example of Multiple Beginnings and Endings ........................................ 16

A-1. Address Options ................................................................................ A-1

1. Bit Period Values ....................................................................................... 8

2. Instruction 101 ......................................................................................... 10

3. Input Frequency (kHz) at Which Processing Time Equals Measuring/

Storing Time ......................................................................................... 14

4. Sampling Interval (Seconds) to Accumulate 8000 Unprocessed Events

for Functions 1,2,6,7 ............................................................................. 15

5. Definition of Test Memory Option Output .............................................. 19

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SDM-INT8 8 Channel Interval Timer

FIGURE 1. SDM-INT8 Front Panel

1

SDM-INT8 8 Channel Interval Timer

1. Overview

The 8 channel Interval Timer (INT8; see Figure 1) is a measurement module
which outputs processed timing information to a 21X, CR10(X), CR23X,
CR800, CR850, CR1000, CR3000, CR5000, or CR9000(X) datalogger. Each
input channel is programmed to detect transitions from low or high level
voltage inputs (Figure 2). Period, pulse width, frequency, counts, and time
intervals are output to the datalogger for further processing/logging.

FIGURE 2. Voltage Input Options, Edges, and Thresholds

In CRBasic, the SDMINT8 instruction is used to program and control the
SDM-INT8; in Edlog, Instruction 101 is used. These instructions, address,
command, and receive data from the INT8 through three ports on the
datalogger (see Section 3). Multiple INT8s, each with a unique address, may
be controlled by one datalogger.

The INT8 has its own processor which enables it to make measurements and
process data while the datalogger is performing other tasks. Each of the 8
channels may be independently programmed to detect either rising or falling
edges and perform the following functions (Section 5.1.3).

The INT8 can capture timing events with 1 microsecond resolution over a
maximum range of 16.77 seconds. Timing on different channels can be
compared to within ± 1 microsecond. At the same time, the datalogger can be
executing various analog measurements, but the exact time these
measurements are taken is subject to the datalogger's timing resolution.
Section 7.3 discusses the possibilities and limitations of synchronizing INT8
and datalogger measurements.

2

2. Specifications

Operating voltage: 9.6 V to 16 V DC

Current drain: 13 to 20 mA active, 400 microamp quiescent

Environmental: -25 to +50 degrees Celsius 0 to 90% RH (non-condensing)

Number of channels: 8

Maximum timing measurement: 16.7 seconds

Resolution: ± 1 microsecond

Dimensions: 8 x 5 x 1 in (13 x 20 x 2 cm)

Weight: 1.4 lbs (635 g)

Input voltage option per channel: high level, low level

SDM-INT8 8 Channel Interval Timer

High Level Voltage Input

- Minimum pulse width: 2 microseconds

- Signals edges:
rising: transition from < 1.5 to > 3.5 volts
falling: transition from >3.5 to<1.5 volts
Maximum input voltage: 20 volts

- Maximum frequency:

5.1 kHz when using Averaging Options
10 kHz when Capturing All Events

The Low Resolution Frequency function allows higher frequencies to be
measured if it is used on all programmed channels with Execution Interval
Averaging. Maximum frequency is dependent on the number of channels
programmed, as shown below:

No. of Channels
1 42.5
2 17.5
3 11.0
4 8.6
5 5.2
6 4.8
7 4.5
8 4.28

Max Freq (kHz)

:

Low Level Voltage Input:

- Minimum AC voltage: 20 millivolts RMS

- Input Hysteresis: 11 millivolts

- Maximum AC voltage: 20 volts RMS

- Minimum frequency: 1 Hz

- Maximum frequency:

3

SDM-INT8 8 Channel Interval Timer

Minimum AC Max Freq.
voltage RMS
20 mV 100
50 mV 400
150 mV 1000

2.5 V - 20 V 4000

3. Connections

The CABLE5CBL-L cable connects the SDM-INT8 to a datalogger. The
datalogger-to-SDM-INT8 connections are shown in Figure 3. Please note that
the SDM-INT8 connects to the CR9032 CPU module of the CR9000X and the
CR9080 PAM module of the CR9000. INT8s are shipped from the factory
with a 10K Ohm resistor attached to the terminal strip for the convenience of
21X user. This resistor is necessary only when the INT8 is used with a 21X
datalogger.

(Hz)

CAUTION

CAUTION

Except for the 21X, the order in which the datalogger and
SDM-INT8 connections are made is critical. The
datalogger cases and wiring panel bracket are at
datalogger ground. To avoid accidentally shorting 12 V to
the case, connect the 12 V first then the ground. To
prevent voltages in excess of 5 V from entering the
datalogger’s SDM ports (C1 to C3 or SDM-C1 to SDM-C3),
the ports are wired after connecting the ground lead.

For the 21X, a 10K resistor is wired between Control Port 1 and single ended
input 1 (1H). The order in which 21X/INT8 connections are made is not
critical.

The CABLE5CBL-L has a user-specified length. A 1-ft length should be
sufficient when both datalogger and SDM-INT8 are housed in an ENC12/14
enclosure; a 2-ft length may be required if the datalogger and SDM-INT8 are
housed at opposite ends of an ENC16/18. The total cable length for all SDMs
should be as short as possible and preferably does not exceed 20 feet. Longer
lead lengths may be possible for CRBasic dataloggers if the SDMSpeed
instruction is used (see Section 5.1.2). Long lead lengths may prevent
communication.

The signal input lines of the INT8 are protected against the
continuous connection of voltages up to 20 VDC and
against high voltage electrostatic discharge. However,
where there are long cable runs (>3 m) to the sensor and
particularly when the cables run outside, some extra
protection may be required for these inputs to protect the
inputs against high energy surges, as may be induced by
lightning. Please contact Campbell Scientific for further
advice.

4

CR800,
CR850,

CR9032

(CR9000X),

CR9080

(CR9000),

CR10(X),

CR23X,

or

CR1000

CR3000,

CR5000

12V

SDM-C3
SDM-C2
SDM-C1

SDM-INT8 8 Channel Interval Timer

G

10K OHM
RESISTOR

FIGURE 3. Wiring Diagram

4. Power Supply Considerations

The datalogger's power supply is typically used to power the INT8, however,
an auxiliary supply may be used as shown in Figure 3. When selecting a
power supply, consideration must be given to the active current drain and the
active time of the INT8. With two exceptions, if the INT8 is programmed it is
drawing 13 to 20 mA. The two exceptions are:

• When the Specified Averaging Interval (Output Option Section 5.4) is

selected, the INT8 enters the quiescent current drain state (400 microamp
current drain) after returning the results to the datalogger.

• If the interval between executions of Instruction 101 exceeds 16.77

seconds, the INT8 enters the quiescent current drain state.

If a 21X datalogger is used to power the INT8, all low level analog
measurements (thermocouples, pyranometers, etc.) must be made
differentially. This is due to slight shifts in the ground potential on the
terminal strip when the 21X is used to power external devices.

5. Programming the Datalogger

The datalogger is programmed using either CRBasic or Edlog. Dataloggers
that use CRBasic include our CR800, CR850, CR1000, CR3000, CR5000, and
CR9000(X). Dataloggers that use Edlog include CR7, CR10(X), CR23X, and
21X. Both CRBasic and Edlog are provided in LoggerNet and PC400.

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SDM-INT8 8 Channel Interval Timer

5.1 CRBasic Programming

5.1.1 Instruction SDMINT8

The SDMINT8 instruction is used to program and control the SDMINT8
interval timer module. Description of the instruction follows.

Syntax

SDMINT8 (Dest, SDMAddress, Config8_5, Config4_1, Funct8_5, Funct4_1,
OutputOpt, CaptureTrig, Mult, Offset)

Dest: Dest is used to specify the array where the results of the instruction are
stored. For all output options except Capture All Events (-nnnn), the Dest
argument should be a one dimensional array with as many elements as there
are programmed INT8 channels. If the Capture All Events output option is
selected, the Dest array must be two dimensional. The magnitude of first
dimension should be set to the number of functions (up to 8), and the
magnitude of the second dimension should be set to at least the maximum
number of events to be captured. The values will be loaded into the array in the
sequence of all of the time ordered events captured from the lowest
programmed channel to the time ordered events of the highest programmed
channel.

NOTE

SDMAddress: This parameter is used to define the address of the INT8 with
which to communicate. Valid SDM addresses are 0 through 14 (factory default
is 0). Address 15 is reserved for the SDMTrigger instruction. If the Reps
parameter is greater than 1, the datalogger will increment the SDM address for
each subsequent device that it communicates with. See Section 6.1 for further
detail.

CRBasic dataloggers use base 10 when addressing SDM devices.
Edlog programmed dataloggers (e.g., CR10X, CR23X) used
base 4 for addressing.

Config8_5: The Config8_5 parameter is a four-digit code used to configure
channels 5 through 8 on the INT8. Each input channel can be configured for
either high or low level voltage inputs and for rising or falling edges. The
digits represent the channels in descending order from left to right (e.g., 8 7 6

5). As an example, the code 0303 would program channels 8 and 6 to capture

the rising edge of a high level voltage, and channels 5 and 7 to capture the
falling edge of a low level voltage. See Section 2 for information about the
specification requirements of high and low level voltage signals.

Description

Code

0 High level, rising edge
1 High level, falling edge
2 Low level, rising edge
3 Low level falling edge

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Config4_1: The Config4_1 parameter is a four-digit code used to configure
channels 1 through 4 on the INT8. It is identical in function to Config8_5. The
digits represent the channels in descending order from left to right (e.g., 4 3 2

1).

SDM-INT8 8 Channel Interval Timer

Function8_5: The Function8_5 parameter is a four digit code used to program
the timing function of channels 5 through 8. Similar to the Config parameters,
digits represent the channels in descending order from left to right (e.g., 8 7 6

5). See Section 6.3 for further details about these functions.

Description

Code

0 No value returned
1 Period (ms) between edges on the programmed channel
2 Frequency (kHz) of edges on the programmed channel
3 Time (ms) between an edge of the previous channel and an edge of

the programmed channel

4 Time (ms) between an edge on Channel 1 and edge on the

programmed channel

5 Number of edges on channel 2 since last edge on channel 1 using

linear interpolation
6 Low resolution frequency (kHz) of edges on programmed channel
7 Total count of edges on programmed channel since last interrogation
8 Number of edges on channel 2 since last edge on channel 1 without

linear interpolation

Function4_1: The Function4_1 parameter is a four digit code used to program
the timing function of channels 1 through 4. It is identical in function to
Function8_5. The digits represent the channels in descending order from left to
right (e.g., 4 3 2 1).

OutputOpt: The OutputOption parameter is a numeric code that is used to
select one of the five different output options. The selected option will be
applied to all of the INT8 channels. A brief explanation is given below for
each code. See Section 6.4 for detailed explanations of each option.

0: Stores an average of the event data since the last time that the INT8 was
interrogated by the datalogger. If no edges were detected, 0 will be returned for
frequency and count functions, and 99999 will be returned for the other
functions. The INT8 ceases to capture events during communications with the
datalogger, thus some edges may be lost.

32768: Performs continuous averaging, which is utilized when input
frequencies have a slower period than the execution interval of the datalogger.
If an edge was not detected for a channel since the last time that the INT8 was
polled, then the datalogger will not update the Dest for that channel. The INT8
will capture events even during communications with the datalogger.

nnnn: Averages the input values over "nnnn" milliseconds. The datalogger
program is delayed by this instruction while the INT8 captures and processes
the edges for the specified time duration and sends the results back to the
datalogger. If no edges were detected, 0 will be returned for frequency and
count functions, and 99999 will be returned for the other functions.

-nnnn: Instructs the INT8 to capture all events until "nnnn" edges have
occurred on channel 1, until the datalogger addresses the INT8 with the
CaptureTrig argument true, or until 8000 events have been captured. When the
CaptureTrig argument is true, the INT8 will return up to the last nnnn events
for each of the programmed INT8 channels, reset its memory, and begin
capturing the next nnnn events. The INT8 waits for the first edge on channel 1

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