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Water Level FAQ Q: Are there any special application considerations for using the Thalimedes in surface water measurements? A: It is quite common to use the Thalimedes in surface water measurements. In order to use the Thalimedes shaft encoder for surface water, the application will require a water stilling well.
Q: What types of data logging or telemetry does the Thalimedes offer? A: The Thalimedes will communicate directly with a modem. The system has the ability to control commonly used modems such as GSM, Landline, and Cellular technologies. Alternatively, the Thalimedes has an onboard data logger that can hold 30,000 readings.
Q: How is the Thalimedes powered? A: The Thalimedes is available with or without an internal battery. The internal battery (standard C-cell) can last up to 15 months in most applications. The Thalimedes without an internal battery requires an external 12v power source.
Q: What size of well diameter would I need in order to use the Thalimedes? A: The Thalimedes will operate in 4-inch diameter and larger well sizes.
Q: What exactly is the "bubble-in" principle and how does it work? A: A piston pump inside the instrument enclosure generates compressed air, which flows through a dedicated line into the bubble chamber at programmable intervals, where it bubbles out uniformly into the groundwater. Depending on the groundwater level (h) above the bubble chamber orifice, an air pressure equal to the hydrostatic pressure (p) is established inside the measuring tube. p = ρ · g · h Assuming a constant liquid density, there is a linear relationship between the water level to be measured and the air pressure inside the measuring tube. The bubble-line pressure and the barometric pressure are measured concurrently by an absolute pressure-measuring cell inside the instrument enclosure. The water level is calculated as the difference between the two signals. This measuring method prevents a potential zero-point drift of the measuring cell from influencing the accuracy of the instrument. The sage of an absolute pressure-measuring cell makes the instrument completely unaffected by humidity and condensation.
Q: What are the advantages to "bubble-in" technology? A: The primary advantage to this technology is that it is drift free. Adverse affects such as temperature fluctuations are non-existent with the bubblers. In addition to being drift free, the sensors are typically located out of the water, lessening possible damage or flooding of the instrumentation.
Q: How far down does the bubble pot need to be placed? A: The bubble pot, located on the end of the bubble tubing, must remain below the water level at all times.
Q: Is the Orphimedes better suited for ground or surface water level measurement? A: The Orphimedes is designed for ground water applications only and is not suitable for superficial water.
Q: What size well will the Orphimedes fit in? A: The Orphimedes can be placed in 2 inch or greater well diameters.
Q: How does the instrument store data and how many reading can be held? A: The instrument stores data using ring memory (first in first out) and can hold 52,000 readings.
Q: What exactly is the "bubble-in" principle and how does it work? A: A piston pump inside the instrument enclosure generates compressed air, which flows through a dedicated line into the bubble chamber at programmable intervals, where it bubbles out uniformly into the groundwater. Depending on the groundwater level (h) above the bubble chamber orifice, an air pressure equal to the hydrostatic pressure (p) is established inside the measuring tube. p = ρ · g · h Assuming a constant liquid density, there is a linear relationship between the water level to be measured and the air pressure inside the measuring tube. The bubble-line pressure and the barometric pressure are measured concurrently by an absolute pressure-measuring cell inside the instrument enclosure. The water level is calculated as the difference between the two signals. This measuring method prevents a potential zero-point drift of the measuring cell from influencing the accuracy of the instrument. The usage of an absolute pressure-measuring cell makes the instrument completely unaffected by humidity and condensation.
Q: What are the advantages to "bubble-in" technology? A: The primary advantage to this technology is that it is drift free. Adverse affects from temperature fluctuations and barometric changes are non-existent with the bubblers. In addition to being drift free, the sensors are typically located out of the water, lessening possible damage or flooding of the instrumentation.
Q: Is the Nimbus better suited for ground or surface water level measurement? A: The Nimbus can be used for both applications. Typically the system is used in surface water while the Orphimedes is used for ground water. However, coupled with a micro station, the Nimbus can easily be adapted for groundwater applications, especially when telemetry is needed.
Q: What types of communication or telemetry does the Nimbus offer? A: The Nimbus will communicate directly with a modem. The system has the ability to control modems using technologies such as GSM, Landline, and Cellular. Alternatively, the Nimbus has an onboard data logger that can hold 400,000 readings.
Q: Is the Nimbus SDI-12 Compliant? A: Yes. The Nimbus can be configured as a fully SDI-12 compliant sensor and may be used with any common data logger including the OTT LogoSens.
Q: What is the diameter of the OTT pressure sensor? A: The OTT pressure sensor is approximately 3/4 inches in diameter, and will easily fit down a one inch well.
Q: What sorts of outputs are available? A: The OTT pressure sensor will communicate via the SDI-12 standard digital line (water level and temperature) as well as a 4-20 m/A analog line (water level).
Q: What is the FAD box and do I need one? A: The OTT PS 1 pressure probe is connected to the FAD 4 P humidity absorber by a flexible, longitudinally stable cable that contains a pressure compensating capillary tube for the atmospheric pressure. This serves as a connecting point for signals going on further, for connection to external data loggers.
Q: How is the instrument configured? A: The instrument is configured via SDI-12 commands.
Q: Does the OPS measure level or pressure? A: The OPS measures the pressure as well as the temperature. The gravity constant at your measurement site can them be entered manually, which allows the OPS to calculate the water level, which is then reported as the output value.
Q: What level ranges are offered? A: The OTT pressure sensor can be purchased in 5 ranges: 0 to 5m, 0 to10m, 0 to 20m, 0 to 40m, and 0 to 100m.
Q: What are the advantages of non-contact water level sensors? A: Non-contact sensors are often used in surface water applications where debris or major water level fluctuations are expected. By keeping the equipment out of the water, it is protected from debris coming downstream during major events.
Q: What site conditions need to be met in order to obtain accurate readings from a Kalesto Radar Sensor? A: There are only a few requirements: No obstructions should be inside the beam. Avoid reflective areas parallel and also above the Kalesto. The water level in the area below the Kalesto should be higher than ground and there should be no standing waves. It is recommended that you mount the Kalesto at one third of the river width.
Q: What is the angle of the Kalesto's beam? A: The Kalesto uses a very small angle of 5 degrees.
Q: What types of output does the Kalesto offer? A: The Kalesto communicates over RS485 using OTT protocol. The instrument can be purchased with an SDI-12 converter and be used to communicate with any common data logger.
Q: How far from the water level should the instrument be? A: The Kalesto should be positioned at least 2.5 meter (8 ft) above the surface of the water. There is a natural 2.5 meter “dead space” below of the Kalesto. If the water level is expected to reach this close to the Kalesto, an optional reflector can be purchased to reduce this space (Kalesto will be mounted horizontally).
Q: Will the Kalesto work with my data logger? A: By using the SDI-12 converter, the Kalesto sensor can be used with most any data logger.
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