Integrating the Yieldpoint d-exto MPBX

Transcription

1 5 Gould Road, PO Box 2155 New London, NH USA Voice: (603) Integrating the Yieldpoint d-exto MPBX Sensor Application Note #27 Revision 06/08/2017 Overview The Yieldpoint d-exto is a multi-position (1-6) borehole extensometer or MPBX. It differs from traditional MPBX s in that it arrives fully assembled and ready for installation. Typically, it is installed by grouting into a drill hole. The assembly consists of a series of groutable anchors attached to fiberglass rods. These rods are protected in Lexan tubing and terminate in a head assembly which integrates displacement transducers. Transducers are available in several ranges including 125mm, 150mm and 250mm. The transducers measure the relative movement between each anchor and the head assembly. These measurements provide for understanding deformation of the rock being monitored. The head assembly is usually installed at the collar of the drill, but can also be installed at the bottom of the drill hole. Measurements are then relative to the collar or the bottom, respectively, as illustrated below in Figure 1. (Figure 1) Integrated to the head assembly are electronics to read each displacement transducer and convert it to a digital format. A typical measurement response is shown below. :YP, ,d3EXTO,41,+ 19.9,C, 16.12,mm, 16.96,mm, 16.78,mm, <CR><LF> The head assembly also includes a RS-485 half-duplex (2-wire) interface for transmitting the digital string over long distances. A two-wire RS-485 interface is utilized. System wiring is detailed in the following section. Integrating the Yieldpoint d-exto MPBX 1

2 System Wiring and Configuration A converter is typically required to convert the RS-485 output of the d-exto to RS-232. The example wiring in Figure 2 outlines connecting a d-exto to a Campbell Scientific CR1000 using the RSCOM2A converter from RE Smith. The RSCOM2A provides a low-cost, highly configurable signal converter. (Figure 2) Note: Two of the internal jumpers must be moved to from their factory positions to function properly with the d-exto. Campbell Scientific is a registered trademark of Campbell Scientific, Inc. (Figure 3) Integrating the Yieldpoint d-exto MPBX 2

3 Function Test Once all the wiring is complete, it's recommended to test the operation of the d-exto. Ideally this is completed prior to grouting the unit into the drill hole. A 12V power source is required for the d-exto and the RSCOM2A. A 12V battery works well. Wiring is shown previously in Figure 2. Connect the serial cable from the RSCOM2A to a computer using a straight-through serial cable. Launch a terminal emulation program such as HyperTerminal on the computer. Configure the port to match the physical port being used on the computer to connect to the d-exto. Serial port settings are shown in Figure 4. (Figure 4) If the connections and serial configuration parameters are correct, the terminal window will display the measurement strings from the d-exto, as shown in Figure 5 below. HyperTerminal is a registered trademark of Hilgraeve, Inc. (Figure 5) Integrating the Yieldpoint d-exto MPBX 3

4 The fields of the string in Figure 5 are as follows: : YYMMTTDDD, where YYMM is the year and month of manufacture, TT is the type where the first digit is the number of anchors + 1 (e.g. 4 = 3 anchors), and DDD is a manufacturing ID. D3EXTO: Type of instrument where the numeric value indicates the number of positions. 41: First digit is number of channels + 1, second digit is type where 1=displacement, 5=load. 23.0: Head temperature in degrees C : Absolute displacement in millimeters. (First value is sensor closest to head.) mm: Units of displacement. MultiLogger Configuration Several gage types were added to support reading the d-exto. Contact Canary Systems if your installation of software does not list the required gage types. Note: The d-exto communicates via RS-485, however it does not support any networking, so multiple d-exto nodes cannot use the same cable for communications. Separate RS-485/RS-232 adaptors and separate COM port connections are required for each d-exto. This limits the number of sensors that can be supported be each datalogger. For the Campbell CR1000 MCU the maximum would be 5, utilizing COM1-COM4 and the RS232 port. For the Campbell CR800 MCU the maximum would be 3, utilizing COM1-COM2 and the RS232 port. Direct Connect Channel Configuration Typically, the Direct Connect Channel Configuration would be used for configuring the d-exto s. However, since Direct Connect channels are limited to 16, and each position requires a channel, if the system must read more than 2 d-exto s with 6 positions each, there are insufficient channels. In that case, use a multiplexer configuration, the following section will detail that configuration. Add a Campbell CR1000 MCU to the network, double-click to load the Logger form. Then, select the Direct Connect option on the Program tab, as shown in Figure 6. Canary Systems is a registered trademark of Canary Systems, Inc. (Figure 6) Integrating the Yieldpoint d-exto MPBX 4

5 This displays the Channel Configuration form. Note the Gage Type Make Model selection for Channel 1. The Units Conversion may also be used to convert the units. The default output of the d-exto is millimeters. (Figure 7) To read the temperature output of the d-exto, configure the Upper Channel. (Figure 8) Integrating the Yieldpoint d-exto MPBX 5

6 Subsequent channels would be configured with each d-exto position. An example for channel 2 is shown in Figure 9. Multiplexer Configuration (Figure 9) If more channels are required than can be supported using Direct Connect configuration then a multiplexer may be configured. The multiplexer configuration simply acts as a placeholder for the measurements. Use the Multiplexers button on the Program tab to display the Configure Multiplexers form. Select Virtual as the Model and Digital as the Gage Type, as shown in Figure 10. The Channels configuration will determine how many channel placeholders will be available. If the temperature (Upper Channel configuration) of the d-exto will be read then the maximum Channels will be 16 x 4 Wires. If no temperatures are to be read the maximum Channels will be 48 x 2 Wires. (Figure 10) Integrating the Yieldpoint d-exto MPBX 6

7 Press the Edit Channels button to configure the channels. Channel configuration is similar for Direct Connect configuration. An example for channel 1 is shown in Figure 11. (Figure 11) Once all channels are configured, press Start/Update to create the MCU program, download it and start the Monitor mode. Note: Typically a Zero Reading would be configured for each channel to output relative anchor position change. (Figure 12) Integrating the Yieldpoint d-exto MPBX 7