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Gilson Engineering Sales, Inc. 

 

November, 2011 4
Articles
Gilson Wireless Solutions
Ringback in Ultrasonic Level Sensors
Tech Tip, Why use Temperature Transmitters
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BrainChild Digital Recorders

  Brainchild VR06

The BrainChild line of paperless recorders is available for less than $2,000 for the 6 input unit. These paperless recorders can be setup to accept 6, 12, or 18 analog and/or digital inputs. The inputs can be Milliamp, voltage, thermocouple or RTD. All data values can be stored on a flash card and sent to your control room via Ethernet, RS-485, or RS-232. This allows you to send emails or text messages for alarming purposes.  The lead time is under one week.

View VR06 datasheet

 

We offer a 6.4" high resolution color display (640 x 480 pixels), versus the industry standard of 5" with 320 x 240 pixels. The screen has an infrared detector that will turn the display off and go into screen saver mode after a set amount of time (standard is 10 minutes - this can be changed or turned off). The screen comes back on when movement is sensed, to save energy.  

Brainchild Paperless Recorder Introduction Video
Brainchild Paperless Recorder Introduction Video

 

Gilson Wireless Solutions
 

Gilson Engineering has a wide range of products for wireless applications.

  

For the Point to Point application where expansion is not likely to occur, the Banner DX 70 pair handles the application. Units are able to send and receive signals (transceivers) whether discrete or analog. Banner DX70

 Banner Point to Point Radios

  

The Point to Multi-Point units are similar to the Point to Point units except one gateway system controller unit may monitor up to 56 nodes that monitor and/or control I/O in remote locations.

Banner Multipoint radios

 

Elpro WIBFor Databus Gateway applications, interface units connect to various fieldbuses. Ethernet, Modbus, Profibus, DF1, DeviceNet and Modbus Plus are available.

Elpro Wireless Gateways

 

Elpro wireless meshFor Mesh Network applications Elpro 915u-2 units are available for both the Gateway and nodes. The wireless mesh structure enables every wireless gateway/transceiver to act as a repeater.

Elpro wireless mesh

   

OmniSite offers 3 different monitors from the Viper to the XR-50 to the Crystal Ball, all of which relies on a combination of cellular telephone and Web-based technology. Each unit is capable of sending a wireless signal to the local cellular tower. That signal is bounced to OmniSite's Web interface. When an alarm is triggered, identified operators are contacted immediately via text, email or phone message. The GuardDog interface is a web based software program that allows online access to equipment status from any one of OmniSite's alarm monitors.

More info on Omnisite

 

 

  Ringback in Ultrasonic Level Sensors

 

One of the more common causes of ultrasonic level sensor errors is a phenomenon known as ringback. Ringback is an installation problem that gives the customer a false high reading or alarm.

 

Since the ultrasonic transducers use a sound wave to calculate the distance to the level, they need to vibrate internally to create that sound. The transducer receives an electrical pulse from the transmitter causing the transducer to vibrate. When the electrical pulse has ceased, the transducer continues to vibrate. This continued vibration is ring down. During this period of time known as ring down, the ultrasonic system is unable to measure. Basically, the sensor is still ringing when it is trying to listen for a return echo.

 

Ringing can be prevented by following a few installation guidelines:

 

  1. Do not over-tighten the transducer. By over-tightening, we cause the transducer, coupling, and mounting device to vibrate, causing extended ringing. This rule applies to both thread and flange mount transducers. You should tighten a transducer only finger snug where possible according to the area codes.
  2. Use a non-metal mounting material. Plastic or rubber does not ring as well as metal. By placing a non-metallic coupling on a thread mounted transducer or inserting a non-metal gasket on a flange mounted transducer, we can reduce the ringing.

Temperature can add to this problem. When installing a transducer in an area where there will be temperature swings, it is even more important to follow the mounting guidelines. As temperature decreases, the mounting becomes tighter as the material shrinks. This also can increase ringing.

 

For more troubleshooting tips with ultrasonic level sensor, take a look at the following video.

Siemens Hydroranger Troubleshooting video
Siemens Hydroranger Troubleshooting video

 

Tech Tip

What are the advantages of using a temperature transmitter over direct wiring a sensor to a PLC or DCS?

 

Cut Wiring Costs

Direct wiring sensors to a control system requires the use of sensor extension wires, which can be three times more than the common shielded copper wire used for a temperature transmitter's 4-20mA signal.

 Temperature transmitter 1A

Protect Signals from Plant Noise

In a direct wiring scheme, the low-level signals generated by an RTD (ohm) or thermocouple (mV) are particularly susceptible to the signal degrading effects of RFI/EMI. A temperature transmitter converts a sensor's low-level signal to a high-level analog signal (typically 4-20mA).

 

Stop Ground Loops

Make sure to choose an isolated transmitter. Input/output/power signal isolation protects against signal inaccuracies caused by ground loops. This is important even when using un-grounded thermocouples because their insulation will eventually break down.

 Temperature transmitter 2

Reduce Hardware Costs

With direct wiring, it is necessary to match the sensor type to input-specific DCS and PLC input cards. Sensor  input-specific  cards usually cost a lot more  per point than a 4-20mA input card.

 

Enhance Accuracy.

A microprocessor based temperature transmitter can be scaled over a wide or narrow temperature range. The accuracy of Thermocouple or RTD input cards is a percentage of the entire temperature span. You won't get very good accuracy if you want to measure a span of 100 deg F on an input card with a range of -200 to 1,500 deg F.

   

Click for more info on Signal Isolators