Moisture Frequently Asked Questions
No moisture sensor is accurate in all materials. They must all be checked after installation.
We always recommend the most accurate method, to ensure your satisfaction with the results.
Sometimes yes, sometimes no. If the material is similar to sand (density of 80 to 150 lb per cu. ft.) and moisture range is 1 to 20% full scale, there should be no problem, AS LONG AS YOU RECALIBRATE IT! If its density or moisture range is widely different, however, you may not have enough adjustment range. Ideally, you should contact our plant for advice. If the sensor has not been shipped, we can set it up for the material; we have many samples already and we test new materials frequently. If we have no experience with your material, we will ask for a sample. This ensures that your sensor will not only work but will be approximately precalibrated when you receive it.
If you have a range of materials, each with its own sensor, they should all be set up in this way. If you need to keep a spare sensor for replacement, it may be suitable for some but not all of the materials. Again, call us for advice.
Our advice is free – take advantage of it before you take delivery.
Some batch controllers correct the aggregate target weights on the subsequent batch, based on the moisture value measured on the previous batch, while others recalculate the target during the weighing period, based on the current moisture value. Both systems have their merits and both can use the “sampling” mode of operation. In this, the moisture averaging starts when the feed gate opens and continues during the fast and slow or jogged feed. The analog output updates continuously and the controller can take a reading at any time. This is much better than using the “continuous” mode, which has a built-in response time of several seconds. Consequently, it limits the accuracy when you require immediate results.
The SAMPLING mode is the best for both on-the-fly and next batch measurement.
Both have their place and many times you don’t have a choice. Most of the North American batching computers use the 0-10V standard while most PLC based systems (like our BatchTron) use 4-20mA. Unless you must choose the 0-10V standard, always use 4-20mA; it is slightly more accurate, especially over long cable runs, and allows connection of both the batch controller and the digital display if needed (in series). The digital display requires 4-20mA as its power source and will not operate on 0-10V.
Always use 4-20mA when you can.
Both the RS232 (one sensor only) and the RS485 (multiple sensors on one line) use the same protocol, which is “industry standard”. If your control system is already compatible with others using digital connection, it will connect to AquaSense and operate in the same way as with other sensors. The setup and calibration software uses a different protocol however, and you need to install the Scale-Tron GUI software in order to change adjustments.
AquaSense uses ‘Industry Standard’ protocol and is compatible with most controllers.
AquaSense 2280D is rated for sensor body temperatures up to 120 degrees F (50 degrees Celsius). Above this temperature, accuracy will be impaired and above 200 deg. F ( 93 deg. C), the electronics will cease to function. You can protect the sensor by installing it in a tube, mounted within the bin, at our recommended angle and insertion depth. You must seal the tube to the outer rim of the sensor at its far end. The tube must be wide enough to allow free circulation of air. Provide a free circulating or forced air supply to keep the AquaSense 2280D body temperature as low as possible.
In extreme cases, replace the air tube with a 1/4″ to 3/8″ copper water pipe coiled around the portion of the sensor inside the bin and run water through it. The ceramic faceplate can reach 100 deg. C. continuously but above this temperature the silicone sealant will deteriorate.
These techniques will allow operation in steam heated aggregate bins and in hot foundry sand, plus many other applications. Call for more details or download application note.
Hot materials require special installation precautions. Call us.
The simplest way is to use a separate digital display for each sensor. The panel-mount sensor is suitable for installation in a small cabinet or large control panel. Alternatively, you can use a single display for many sensors, with a rotary switch to select one bin at a time. If you need a computer display, the RS485 connection can easily connect many sensors together, into a single serial port on the computer or PLC. In this case, you need to develop some simple software to use it. Alternatively the calibration and monitoring software can read all the sensors continuously. Call us for advice if you need something a little different.
Whichever way you want to do it, it is simple. Call us for details.
The AquaSense can be calibrated for many different materials. These calibrations are stored in the sensor’s memory and can be retrieved through the digital RS232/RS485 connection.
AquaSense solves problems that could not be solved before.
Several customers have had premature failures of their AquaSense 2280D sensors; typically the circuit board shows burn marks under one or more chips, plus damage to the microwave sensor. This is most likely due to a poor ground connection between the control cabinet and the plant frame. Voltage surges (usually due to nearby lightning) entering the control cabinet through the power or phone lines find the shortest path to ground, which is through the AquaSense 2280D or load cells. The solution is to install a short, thick ground conductor between plant frame and control cabinet to hold both at the same electrical potential. No sensor is immune to this type of damage, but it can be minimized.
See our Tech tips page for more details and moisture frequently asked questions.