Skip to Content

SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

SiePortalDeutsch

Search

Home
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menu temporary not available
- Menue temporary not available
- {{item.title}}

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

Inaccurate cablelength distance using the BT200

Created by: gmb at: 8/29/2008 7:52 PM (5 Replies)

Rating (2)

Thanks 0

6 Entries

8/29/2008 7:52 PM	Rate (0)
gmb Posts: 3 Rating: (0)
gmb Posts: 3 Rating: (0)
Suggestion To thank Quote Answer

8/29/2008 8:28 PM	Rate (0)
gmb Posts: 3 Rating: (0)	When using the BT200 i amgetting a cablelength distance more then twice of the reflective distance.I am seeing the condition on 40% of the 60 systemsI tested.When doing repeated test on the same system sometimes it works OK. i checked connections repeatedly without any good results.We are using Turck interfaces. also used Step 7 Topology test to confirm lenght. Any thoughts. Glen attached is BT200 test results with repeated cablelength test. Attachment OP40-9 RE-TEST 8-26-08 BT200.pdf (348 Downloads)
gmb Posts: 3 Rating: (0)
Suggestion To thank Quote Answer

8/30/2008 8:01 PM	Rate (1)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, Is the cable type measured always the same? Because the length is dependent on the resistance set in the BT 200. Do you measure with powered or unpowered devices? If the problem remains, I would try with disconnected devices (to avoid that capacitors must be loaded by the BT200 during measurement, what can impact on the measure). Here some extract of the manual. Distance measurement can only detect lines longer than 15 m. No distance measurement can be performed when repeaters are used. Performing the test: ================== Turn off the power supply of all bus stations. Connect test plug connector to one end of the line and the BT 200 to the other end. (Turn off resistor for BT 200.) Start distance measurement. After the start, the BT 200 requests three values which must be entered on the keyboard. - Loop resistance (default = 110 Ω/km) The default value can be changed via menu item Service. - Number of 12-Mbaud plug connectors/ devices with longitudinal inductivity - Resistance value per connector/device (default = 0.32 Ω) After entry of the last value and confirmation with OK, measurement is performed.
	Last edited by: edr at: 8/30/2008 8:15 PM Last edited by: edr at: 8/30/2008 8:02 PM Best regards jklm Suggestion was helpful? Feel free to rate it.
Suggestion To thank Quote Answer

8/30/2008 11:27 PM	Rate (1)
J_Bell Posts: 5822 Rating: (412)	Hello, well... I admit, I am not sure. If I remember the times with triaxial Ethernet cable we had to use reflectometers to measure distances to a fault in a triax cable. These devices used analogue measurement systems that have been really complex and resource consuming. Devices that did such measurements cost about 50000 € each. If I compare this functionality with the BT 200 at this price... I do not know. To get such a cable test requires a specific environment at certain conditions... well, this is certainly not always possible. There are certain devices on the Market to test PROFIBUS Networks quite well... but most of them analyse the traffic, do they test the physics as well... just seen in the point in measuring reflections created by bad cable sections??? I do not know. I admit, I can not know all of them. Maybe there are some... Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
Suggestion To thank Quote Answer

9/2/2008 2:17 PM	Rate (0)
gmb Posts: 3 Rating: (0)	It appears I am getting two distinct cable lengths. In the example below, the 36 m length is probally acturate.The Higher length is allways the same, even when getting different line resistance. Results Test number Line resistance (Ohm) Distance (m) Notes 0 8.53 88 1 8.53 88 2 9.99 89 3 6.59 88 4 6.59 88 5 6.5988 6 4.17 36 7 4.17 36 8 6.5988 9 10.43 88 It does not appear that the length is dependent on line resistance. Test configuration Baud rate Contact resistance per plug connector Loop resistance PROFIBUS line 187,5 kBaud 0.32 Ohm 110 Ohm/km The system is using Siemens interfaces with Turck Field I/O. Could this cause a problem? GMB
gmb Posts: 3 Rating: (0)
Suggestion To thank Quote Answer

9/2/2008 3:11 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Dear GMB, have you tried to figure out if the reflection test worked out with your Cable segment yet? Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on