EIA (extras)

Question 2

What are the main components of a typical continuous environmental monitor?

Answer 2

• Transducer/probe
• Intelligence-Data Logging Component
• Communications system
• Display / Storage Unit / Computer

Question 3

What is a transducer and how does it work?

Answer 3

The transducer (or probe) is the component that actually quantifies the environmental variable being tested by converting a monitored parameter into a particular quantifiable parameter, such as a voltage level.

Transducers perform this task in a variety of ways depending on what is being measured. Common parameters used include:

• Resistance (pH, temperature)
• Conductivity (pH)
• Light reflectivity (metal concentration, temperature, pH, dissolved oxygen, etc.)
• Generated EMF (estimating ground movement, etc.)
• Mass (deposition gauges)

A number of transducers are not simple electronic probes that measure physical properties:

• Some transducers slowly react with their surroundings, and the rate of the chemical reaction is measured.
• Some transducers work by carrying out periodic chemical test, as opposed to continuous chemical testing. E.g. a given quantity of water may be pumped periodically into a reaction vessel, a known quantity of reagent is added, a chemical reaction occurs, which is monitored in the vessel by a physical property transducer, the data from which can then be used to calculate the desired parameter.

Generally several transducers can be placed in one sensor head or assembly, therefore if one was monitoring the wind direction with a wind direction transducer it’s more than likely that the system would measure temperature and wind velocity all within the same sensor assembly.

Question 4

The power for these transducers can come from a variety of sources, such as:

Answer 4

• An internal battery (suitable for transducers with very low power demand),
• The data logging/intelligence component,
• Telemetry connection (i.e. from the power supply of telephone line in the case of a modem link),
• Power source on site, such as solar or mains electricity (suitable for transducers with a very high power demand).

Question 5

What tasks take place within the electronics of a transducer (i.e. what is the purpose of the Intelligence-Data Logging Component of the environmental monitor)?

Answer 5

1. Traditional analogue instruments (in electronics hardwire) and modern digital equipment (in the microelectronics) correct and calibrate the transducer signal for non-linearity under a particular set of operating conditions.
2. The increasing trend in the use of micro-electronics/micro-computing based equipment is mainly for the processing and interpretation of the signal to be performed at a higher level of ‘Intelligence’. This has several advantages:
   
   • The transducer can monitor parameter(s) continuously but only start to record data when
     it rises above a threshold value (monitoring of ground movement),
   • The frequency of measurement can be varied for different times of year, day etc.,
   • Onboard diagnostic checks can be performed,
   • Instruments in some cases can be self calibrating,
   • Instruments can store quantities of information, acting or combined with a data logger.

The complexity of this part of the monitoring instrument varies greatly. Not all instruments require the same level of complexity.

Question 6

One of the most important aspects of continuous monitoring is how the data is stored or transmitted (by the communications system) once it has been generated by the transducer sensor.

This area is generally referred to as the telemetry operation of the sensor. A variety of telemetry systems exist and are utilised by current monitoring systems. These include:

Answer 6

• In built data loggers
• Hardwire communications
• Modem communications
• Radio communications

Question 7

‘In built data loggers’ is a telemetry system utilised by many current monitoring systems.

What is it and how does it work?

Answer 7

• This is one of the most common approaches and is often found in combination with the other telemetry systems e.g. a data transmission system
• The data logger is basically a small computer that stores the data the environmental sensor produces.
• Additional information such as the time of the reading and a variety of simple calculations can be performed (such as calibration information) on the data as it is logged.
• This information can then be extracted from the logger, by physical examination (if the logger has a display), by computer interrogation, or to another computer via a communications system when requested.

Question 8

‘Hardware communications’ is a telemetry system utilised by many current monitoring systems.

What is it and how does it work?

Answer 8

• This is one of the most simple methods of data transmission and is commonly found in industry on a variety of equipment.
• The sensors can be directly hard wired, or indirectly wired via a data monitoring equipment several miles away from the measured parameter.
• The data can be passed to a variety of monitoring devices, from simple analogue plotters, to record the data, or directly to computer databases.

Question 9

‘Modem communications’ is a telemetry system utilised by many current monitoring systems.

What is it and how does it work?

Answer 9

• This type of system rotes around the sensor being linked via a data logger to a modem and then intern to a phone line.
• The data logger is then periodically interrogated by a computer, connected to a second modem, which requests the information from the logger.
• The information is then downloaded to the main computer.

Question 10

‘Radio communications’ is a telemetry system utilised by many current monitoring systems.

What is it and how does it work?

Answer 10

• This is not a new system but due to the advances in digital data transmission technology, is becoming increasingly used.
• This system can work in a variety of ways in that it can act as a permanent link between the transducer and the information storage system (a computer or paper plotter etc.) like the hardwire system or like the modem system periodically transmit the information to a storage system.
• The main problem with the radio communications system is obtaining a license to utilise a radio frequency.