At the heart of any control system lies the Simplified Control System (SCS™). Individual components may be added or subtracted to the SCS to create and support the proper system functions required to accommodate various operational requirements, including environment stabilization of temperature and humidity, toxic/combustible fume regulation, security monitoring, fire protection and light level conditions.
Components are selected, tested and integrated into the system to stress reliability, ease of operation and low maintenance.
Individual Components of an SCS will vary, but will include some if not all of the following:
Sensor Networks:
Environmental Monitoring –
- Ambient Relative Humidity and Temperature (Dew Point Available)
- Space or Process Control (RH-T)
- Combustible Fumes
- Light Levels (LUX)
- Door Interlock Sensors
Machine Performance and Condition Monitoring –
- Machine Performance Monitoring
- Runtime and Meter Monitoring
- Monitoring of Equipment Fault Conditions
SCS Unit Controllers:
- Extended Operating Range Devices
- Small to Large Data Logging Capabilities
- Some contain Web Services built in
- All are firmware reprogrammable by LTi to meet requirements.
Communications: LTi has a number of Communications options that allow for remote access into the system(s) for data review and system configuration. Options exist for:
- Standard Modem via Standard Telephone connections
- Wireless Cellular (analog and digital)
- Wired and Wireless Internet Remote communications coupled with one of our service contracts provides a powerful package to assure your operations.
Sensor Network:
Environmental Monitoring -
- Ambient relative humidity and temperature (RH-T). An RH-T dual-function instrument is located outdoors in general proximity to the system. The sensor is shielded and protected. This prevents rain from saturating the sensor element and keeps birds and insects from fouling. This type of sensor is primarily used to gauge the difference in ambient and internal conditions.
- Process Control (RH-T). Logis-Tech experience has shown that a minimum of two RH-T sensors should be used for process control. Redundant Sensors provide back up in the event of an instrument failure and allow for greater air sampling providing more uniform envelope coverage. A probe sensor is mounted in the air handling inlet duct for accurate sensing of the zone or shelter condition. A second RH-T sensor, usually wall-mounted, is placed on the opposite end of the zone/shelter from the air inlet. Both sensors are then continually monitored. If either sensor detects relative humidity or temperature outside the acceptable ranges, signals are sent to the HVAC, Dehumidifiers or both to turn on. The integrated unit will run until both sensors values detect an acceptable internal relative humidity or temperature condition. Our higher end controllers are able to react to failed sensors automatically and switch into standard timer based control mechanism until repairs can be made.
- Combustible Fume Sensor (CF). Fuel in preserved vehicles is the most probable fire/explosive hazard in CHP shelters. Therefore, a combustible fume sensor, calibrated for carbon-based particulates, is mounted in the inlet of the dehumidifier (Figure 19). The instrument provides an air sampling, at least once per second, and reports in percent (0 to 100) of the Lower Explosion Limit (LEL) to the controller. The system is alarmed at 10% LEL which will override the relative humidity or temperature control of the integrated unit and will not allow the system to run while in automatic mode. The machine will turn off if running or will not be able to run until the CF level returns to below 9% LEL. A 1 percent dead band prevents the equipment from short cycling and causing damage.
- Door Interlock Sensors. Electro-magnetic switches are utilized as door open/shut sensors to reduce energy usage. Systems are not allowed to run with open doors. It may also be used in tandem with an intruder detection system to trigger alarms, including telephonic, visual, and audible communications.
Machine Performance Monitoring -
- Process Control (RH-T) A relative humidity and temperature (RH-T) sensor is mounted in the process air out duct to monitor the reduction of RH being output by the ADU in the drying cycle. Temperature is also used as a monitored parameter for the purposes of desiccant wheel performance indication and assessment of performance.
- Process Control (T) A temperature (T) sensor is mounted in the react air out duct to monitor the heat being output by the ADU. Reactivation temperature is used as a monitored parameter for the purposes of desiccant wheel performance.
Most sensors used in the SCS network share the following characteristics:
- Temperature accurate to .5 degrees C
- RH accurate to 2 percent typically less than 1 percent drift over 5 years
- Sensors receive power for operation through same cable as network
- Sensor elements are isolated from electronics for more accuracy
- Operating Characteristics:
- Sensors can operate in the following environmental conditions:
- 0 to 70 C
- 0%-95% RH non-condensing
- Operates off of 10-28 VDC or 9-24 VAC
Wireless Sensors are Available for Relative Humidity and Temperature Monitoring
SCS Unit Controllers:
- Distributed input/output (I/O) programmable process controllers collect sensor inputs and transmit control outputs.
- Accept multiple types of sensor input and data types
- Industrial surge protected where and when required
- Able to operate independently or as part of larger network
- Critical process inputs are continuously monitored and algorithms provide full-time control at least once per second. In many cases actual logic proceeds through algorithm up to ten times per second.
- Operating Characteristics:
- Sensors can operate in the following environmental conditions:
- -20 to 70 C
- 5%-95% RH non-condensing
- Operates off of 24 VAC or VDC Nominal (21 to 28 VAC/VDC Actual)
- Wireless Controllers are Available
Communications:
- Remote Network Interface
- Modem This device in an SCS provides one of the “portals” to permit remote monitoring.
- Baud rates up to 56k are supported, rates as low as 14.4k can be utilized as well for older equipment.
- Wired Telephone Supported
- Wireless Cellular (Analog and Digital) Supported
- Internet Adapter If internet connections are available links to 10Mbp can be supported. Protocols for Lonworks, WWW, FTP and Telnet are utilized. All services can be set as dynamic or fixed and all can be password and user account protected.
- Hard-line and Wireless Internet connections supported
- Local Network Interface – A properly equipped laptop or a network service tool can be attached to various locations of the network system and have access to any other part for monitoring or configuration. These interfaces can transfer up to 400 messages a second at up to 78 kbs.