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Data Logging Solutions - SMS Log

Supplier: Sphere Systems

The SMS log is a remote data-logger that also allows for switch operation. It contains 4 digital inputs, 4 analogue inputs and 5 digital outputs.

Price Guide: POA

Inputs and outputs

4 digital inputs. The inputs require dry switching to ground to become activated.

4 analogue inputs with 8 bit resolution and a full scale range from 0 to 5Volts.

5 digital outputs capable of sinking up to 100mA each at 50V maximum Reverse voltage clamping diodes are incorporated into the logger.

Digital inputs

A contact closure to ground will generate an alarm condition. Internal switch de-bouncing can be turned on or off resulting in an activation time of 1s when de-bouncing disabled and <3s when de-bouncing is enabled.

Analogue inputs

Each analogue input can be individually configured for either switch operation (alarm is generated when the input is greater than a preset threshold) or window operation (alarm is generated when the input is greater than an upper limit or lower than a lower limit). Inverted operation allows for these conditions to be inverted. Hysteresis can be applied to the upper and lower limits. The limits and amount of hysteresis are programmable. Engineering units are used when configuring the logger range. Current data is displayed in engineering units when the Data Tracking software is used.

Each input can also be set to operate over a 0-5V range or 4-20mA range (this needs an external 250ohm resistor connected from the input to ground).

Alarm transmission

The logger has a maximum capacity of 4 telephone numbers of up to 16 digits each. The alarm system can be configured to send each alarm to any combination of these phone numbers. The logger will send a common site message for each alarm together with a message specific to that alarm. All messages have a maximum length of 16 characters and are user programmable.

The logger is capable of coping with problems in the GSM network. If an alarm cannot be sent then the system will retry sending the alarm a number of times with a delay between each attempt. If after all attempts have failed the alarm will be discarded. Both the number of attempts to send an alarm and the time between retrying to send alarms are user programmable.


All analogue inputs are logged at the same time. The logging interval can be set as one of the following:

Logging occurs at the cardinal points.

Each frame of data is time stamped with the day, month, hour and minute

Alarms are also logged whenever they are processed for sending. Each alarm is also time stamped with the day, month, hour and minute and in the case of analogue alarms the analogue value of the input is also recorded.

Up to 4032 frames of data are stored which allows recording every 15 minutes for 6 weeks. Both logged and current data is displayed in engineering units when the Data Tracking frontend program is used.

Error protection

All commands which configure the logger and the transmission of logged data are protected by a 16bit cyclic redundancy check character. Commands which read the device status or other information from the device do not have this protection thus allowing the information to be read from the logger using a standard terminal.

SMS commands

The logger is capable of handling a variety of commands sent from a mobile phone using the SMS message service. Each command received from the SMS service will result in an acknowledgment being sent back to the originating caller. The form of this acknowledgment depends on the type of command sent.

A user defined 4 character PIN number is required to be sent as part of the SMS message. This pin number can use any combination of numbers, upper case letters, lower case letters and some symbols resulting a total of about 40,000,000 combinations.


82.5mm W x 82.5mm L x 20mm H

Power supply

Nominally 12V DC but the board will operate from 9VDC. Over voltage protection and reverse polarity connection are incorporated and the board can withstand input voltages up to 70V DC making it suitable for vehicle operation.


A Windows-based PC front-end program is provided which can configure the logger and modem and read the current logger status and logged data. The logged data can be stored in a Microsoft compatible .csv file for use with Excel.

Battery Life

The real time clock uses an onboard battery for backup. Battery life is typically in excess of 2 years of un-powered operation. The logged data has a retention time of >200years without power being applied.