Modular Unit

The CM-3 Pressure Monitor is designed as a successor to the Alert CM-2 monitor which has been in production for over 10 years. The CM-3 will have new features based on Customer feedback and has been manufactured in a format that is more versatile and hard wearing.

Overview

The CM-3 Pressure Monitor is designed as a successor to the Alert CM-2 monitor which has been in production for over 10 years. The CM-3 will have new features based on Customer feedback and has been manufactured in a format that is more versatile and hard wearing.

The unit is designed to monitor the negative pressure difference between atmospheric pressure and the ambient pressure within containment enclosures during the removal of toxic or dangerous substances. The unit gives an audible and a visual alarm if the pressure difference becomes too high or too low and the results are plotted as a graph of pressure versus time using a dot-matrix printer. The standard unit operates on 110v electricity supply but a 240v version and one which has an internal battery for use as a standby power source or for portable operation, are available at extra cost.

The existing range of Power Switching Units and Remote Klaxons are compatible with the CM-3 unit. The Power Switching Units are controlled from the Pressure Monitor and can be used to switch on auxiliary Air Movers or other mains equipment when there is a problem with the pressure. The Remote Klaxons provide a higher sound output for the audible alarm and can be supplied to either sound continuously until the pressure is normalised or be silenced when the mute pushbutton is pressed. A full list of available additional features appears below.

ENCLOSURE

The unit is housed in an injection moulded, "Pelican" style reinforced plastic case designed to protect the instrument from harsh conditions. When closed the case will withstand abuse in almost any environment and will not corrode or dent. It can withstand high temperatures and immersion in water. The case colour will not scratch or rub off and there are moulded recesses for Customer labels.

The case opens by releasing two catches and is operated standing upright (like a book). The controls and displays are mounted on an internal plate and there is space within the lid area to store 6mm nylon pipe. There is also a cable stowage area to store the electricity supply connection cable.

PRESSURE MEASUREMENT AND ALARMS

The pressure is sensed by a solid state transducer and the output from the transducer is converted to a digital word and interrogated by the microprocessor. An alarm is triggered by a low pressure, a high pressure or an over-pressure. The low and high pressure levels can be set and stored in four memory locations A, B, C or D. These can then be selected by a four-way selector switch. The unit is delivered with four sets of values ready programmed. The over-pressure level is preset to 40 Pascals or the equivalent value expressed in inches or millimetres of water.

An alarm condition is indicated by a sounder and by LED indicators. During a low alarm the sounder and the LEDs will be pulsed in a slow rhythm. During a high alarm the pulse rate is increased and for an over-pressure alarm the sounder and LEDs are energised continuously. During a low or high pressure alarm the sounder can be silenced but the LED indication will continue until the pressure is normalised. During an over pressure alarm the sounder cannot be silenced and will continue to sound until the pressure is normalised.