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Measurement of levels in tanks is important across many industrial applications. There are many tank monitoring applications, for example fuel monitoring, mining process liquids monitoring, and pipeline corrosion inhibitor liquid monitoring
The monitoring is required for two purposes. One purpose is to make sure the liquid does not run out / the tank does not run dry. Another purpose is to ensure the liquid is being drawn from the tank in line with the expected usage, which is another indicator that the process using the liquid is operating correctly, and is a derived measure of the flow from the tank.
For this application, it would be appropriate to use a pressure sensor, and use the pressure from that sensor to determine the level in the tank. The sensor would be most likely strain gauge technology, sometimes called a hydrostatic sensor.
These sensors can be either vented or non-vented. Vented sensors have one side of the sensor exposed to the liquid being measured and the other side of the sensor open to the air, either directly exposed, or exposed by using a small vent tube inside the cable with a vent to the atmosphere at the termination end of the cable. Non vented sensors need a barometric pressure sensor at the location of the measurement to provide the current atmospheric pressure, which is then used in a calculation to compensate / normalize the pressure reading based on the current atmospheric pressure at that location and at that time.
The casing for such sensors can be either stainless steel or titanium. Titanium is chosen for more corrosive environments. The output of such sensors is usually either 0 to 5 volts or 4 – 20 mA however there are some with SDI 12 or Modbus interfaces.
The diagram shows two methods of connecting the sensor. The first method is to immerse the sensor in the liquid and the cable exits from the top of the tank. The second method is to add a T piece to the output pipe, and the pressure sensor then is attached to that T piece to measure the pressure exhibited at the T piece and this pressure is directly related to the level in the tank.
Some form of communication is required for the telemetry function, either cell phone or satellite. For areas covered by cell phone, this is the most economical choice, and the Neon field units which use cell phone technology is appropriate, either the Neon Metering Module or the Neon Remote Terminal.
If there is no cell phone coverage the Neon Remote Terminal Satellite is another option. As this is a low volume application a small low earth orbit satellite service is sufficient, or perhaps the Neon Remote Terminal Lite which uses the regional beam of the Inmarsat equatorial satellite service could be chosen.
The application is quite a simple one; the tank level should be measured, perhaps hourly, and stored locally and then sent to the Neon Server daily to display the level on the Neon Web application. The Neon Remote Terminal or Module in the field would also have alarms set up based on any unusual condition, for example too fast level changes would indicate a leak and too slow level changes would indicate a blockage. In the event either of these conditions was detected an immediate transmission back to the server could be initiated and an alarm initiated to alert operators of the problem.
As the power requirements are light, the whole system could be housed inside a small pelican case and powered by a set of lithium batteries. The power budget is small as the sensor would be turned on only for the short time needed to take a measurement every few hours. In this configuration a suitable lithium battery pack could power the entire system for up to 5 years.
|Options for Application Specific Instruments / Inputs||Unidata Part Number||Description|
|Hydrostatic Water Depth Probe||6542D-X||PT12 Pressure/Temperature Sensor SDI-12 3.5m, 10m or 20m|
|Hydrostatic Water Depth Probe - Titanium||6542D-X-T||Titanium PT12 Pressure/Temperature Sensor SDI-12 3.5m, 10m or 20m|
|Satellite Telemetry||2023E||Neon Lite Satellite Terminal|
|Options for Neon Telemetry - NRT / RTU / Field Units||Unidata Part Number||Description|
|Cellular RTU 3G||2013F-AB03||Neon Metering Module 3G with Antenna and Li Battery|
|Cellular RTU 4G||2013F-AB04||Neon Metering Module 4G with Antenna and Li Battery|
|Cellular RTU 3G - Industrial||2016F-AB03||Neon Remote Terminal 3G with Antenna and Li Battery|
|Cellular RTU 4G - Industrial||2016F-AB04||Neon Remote Terminal 4G with Antenna and Li Battery|
|Low Earth Orbit Satellite Globalstar||2015E-AB0||Neon Remote Terminal - Satellite Globalstar Modem with Antenna and three Li Batteries|
|Ethernet||2017E-0B0-1 or 3||NRT Ethernet with single or triple Ethernet Ports|
with three Li Batteries
|Equatorial Orbit Satellite - Inmarsat||2018E-AB0-1 or 3||NRT Ethernet with single or triple Ethernet Ports|
with three Li Batteries
|LCD Display||2500E||NRT LCD Display|
|NRT Field Termination Strip||2103F||2015E,2016F,2017E, and 2018E NRT FTS|
|NRT Firmware Option||2303A-8M||8M Extended Memory Option|
|NRT Firmware Option||2303A-8M-CAM||8M Extended Memory & Serial Camera Option|
|NRT Firmware Option||2303A-CAM||Serial Camera Option|
|Options for Neon Application Software - Customer Server||Unidata Part Number||Description|
|Neon Application Software||2302A||Neon Server Software Licence Incl 5 NAL |
|Neon Application Software||2302A-10||Additional 10 NRT Access Licences|
|Neon Application Software||2302A-20||Additional 20 NRT Access Licences|
|Neon Application Software||2302A-50||Additional 50 NRT Access Licences|
|Options for Neon Application Software - Unidata Server||Unidata Part Number||Description|
|Neon Application Software||2301A||Neon Data Initial Subscription Setup Fee|
|Neon Hosting Service||2301A-01||Neon Data Service Fee for 1-50 NRTs|
|Neon Hosting Service||2301A-02||Neon Data Service Fee for 51-100 NRTs|
|Neon Hosting Service||2301A-10||Neon Data Service Fee Metering|
|Options for Conventional Dataloggers / Field Units||Unidata Part Number||Description|
|Standards Starlogger||6004D-11||Red Logger 512K with Alkaline Battery|
|Display Starlogger||6004D-21||Blue Logger 512K with LCD and Alkaline Battery|
|Prologger||7001D-11||Green Logger 1M with LCD and Alkaline Battery|
|Starlogger Field Termination Strip||6103E||6004D FTS|
|Prologger Field Termination Strip||7100E||7001D FTS|
|Starlog V4 Management Software||6308A-AUE||Starlog V4 Full Licence Key|