Axon Knowledge Base Article # 406

How do I test the LabMaster TL-1 for proper operation?

LabMaster TL-1

Question

Answer

As of October 1, 1997, Axon support for the LabMaster TL-1, TL-2, and TL-3 systems officially ended.
(Axon Instruments policy is to provide support for five years after the date we stop sales of a product.)

Please note, we no longer stock replacements parts. Customers who need to repair a board or purchase a new one should contact Scientific Solutions. Note that after a repair, or with purchase of a new board, you may have to re-configure the jumpers to the Axon settings. Use the diagram in this guide to set the jumpers.

Scientific Solutions, Inc.
9323 Hamilton Drive
Mentor, OH 44060
USA
Phone: +1 440-357-1400
Fax: +1 440-357-1416
e-mail: support@labmaster.com
http://www.labmaster.com/

Technical Questions and Answers

1. My TL-1 interface is showing cross-talk and is swapping channels. How can I prevent this?

   Any active input channels (i.e., channels configured in the software to acquire data) that do not have a signal connected (i.e., an open input) will pick up cross-talk. This is normal with the multiplexer used in the TL-1. Either turn off the channel in software or use a grounding plug on unused input channels to prevent this. If there is a signal input to a channel (i.e., there is a load on the channel), it should not pick up any cross-talk in normal operation.

   Channel swapping can have a variety of causes. Channel swapping or skipping occurs in multi-channel data sets when the samples from one input channel appear to move to an adjacent channel when viewing in the software. This occurs because if one data point is lost, the rest of the data get multiplexed to the wrong channel. For more than two channels, the channels migrate through the data buffer. Channel skipping during high speed, multi-channel sampling has been noted under two different conditions. These are:

   1. All 100 kHz A/D modules are rated at 80 kHz when multiplexed (i.e., when you choose to acquire multiple input channels). While many modules will do multiple-channel acquisition at 100 kHz, if 10 or 11 µs conversion times are used, channel skipping may occur.

   2. If the DMA channel used by the LabMaster (usually DMA 1) has problems (e.g., another device uses the same DMA channel or the desired sampling rate is higher than the DMA rate of the computer), channel skipping will occur.

   Therefore, try a slower sampling rate to see if this fixes the problem.

   You may have a problem with your ribbon cables picking up noise. Wrap each unshielded ribbon cable individually in a full-length of aluminum foil, from the back of the computer to the the back of the TL-1 interface.

   Also, there is a hardware patch to the TL-1 LabMaster motherboard. Add a pull-up resistor to chip U27, connecting pin 3 and 14. Originally, this resistor was only added if the chip was a certain type (LS or HC), but this was changed to require this resistor on all boards. The resistor should be 475Ω at 1%, or 470Ω at 5-10%.

   If the above do not help, then there is probably a problem with the A/D converter on the daughterboard, located in the TL-1 box.

2. Timing errors: auto increment error and channel swapping.

   You can try increasing wait states on the LabMaster motherboard. The WS jumper must be connected. The jumper on J5 must be moved to position 8 on the jumper. To help orient yourself, to the right of the J5 jumper you should see the J4 jumper. The far right position on the J5 jumper should be set to achieve the maximum wait states.

   Check the SW 1 switch settings of the daughterboard of the TL-1 system (contained in the TL-1 interface box):

   

   If the settings are correct and swapping in another interface box solves the problem, then the daughterboard is bad. If not, then the cable or the LabMaster motherboard may be bad. Try replacing the cable.

   There is a U27 chip on the LabMaster motherboard. It should have a resistor soldered across it. A 475Ω (1%) or 470Ω (5-10%) resistor can be soldered across pins 14 and 3. This sometimes cures a channel swapping problem.

   Sometimes the slots in the computer are bad and sometimes the contacts of the LabMaster motherboard are dirty. Try re-seating the board or using another slot in the computer.

   The LabMaster may work in the computer if the ISA bus speed is faster than the standard 8 MHz. Although pCLAMP 6.0.4 provides a way to insert 'timing loop' counts for the Digidata 1200 series interface (to eliminate problems caused by a fast ISA bus), these timing loops are not engaged with the TL-1. Contact Scientific Solutions for a motherboard that works in computers with fast CPUs.

3. No output from Analog Out 0
   
   
   1. Make sure that the white round cable is properly connected to the LabMaster motherboard.
      
   2. Use the Test-TL program to check both Analog Out 0 and 1. The Analog Outs are controlled by the AD DAC80 chips. If Analog Out 1 works but Analog Out 0 does not, you can swap the chips.

4. Error message: B0 not set low
   Possible solutions:
   
   
   1. The B0 switch on the front panel of the TL-1 must be set to LO. If it is not, then pCLAMP 6 will not run.
      
   2. The 26-pin flat ribbon cable that connects the TL-1 interface to the LabMaster motherboard in the computer may not be connected properly. Sometimes reconnecting the cable is necessary.
      
   3. The USS 6 chip on the TL-1 motherboard may be damaged. You can try swapping the USS 5 chip with the USS 6 on the TL-1 motherboard.

5. Troubleshooting TL-1 noise problems
   The TL-1-125 is designed to be used with an amplifier with a 100 kΩ loading resistor on the input. In certain situations, where the oscilloscope has a 1 MΩ resistor, incorrect loading will cause the TL ANALOG OUT signal to look excessively noisy.

   A good trouble-shooting methodology is to make sure that NOTHING else is cabled to the basic setup. This means that even instruments that are turned off must be physically uncabled from the setup. Failure to do so can result in ground loops. Also, it is possible for 'downloading' to occur: where a signal finds a path between an instrument that is turned on and one that is turned off. This can cause timing and other problems.

   The simplest initial setup is with the computer connected only to its interface, and the ANALOG OUT signal looped directly back into the ANALOG IN, with no intervening amplifier or scope. Set up Clampex with steps or ramps to look for noise. Use a test protocol with the ±10 V range for the display, i.e., with a HW DAC and ADC gain of 1 V/Volt. You should set the first clock rate to 10 µs to use a 100 kHz sampling frequency.

   If no noise is observed in the above scenario, start cabling back in instruments, one at a time, until the noise reappears. The last instrument added would then be the source of a ground loop problem.

   An option is to break the ground on the cable attached to the ANALOG OUT, or from the offending instrument, to take care of pesky ground loop problems.

   Another possible option is to run the ADC in pseudo-differential mode, where the A/D signal is not referenced to a common ground, but to a common voltage. On the LabMaster daughterboard, area JS is usually set with 3 jumpers for single-ended mode (ground referenced). Although the LabMaster manual does not document this for 100 kHz modules, this may still be valid, where two jumpers are set (without the one closest to the large silver box) for pseudo-differential mode.

   Also, the color monitor can be a source of high-frequency noise, which falls off about 3 feet from the monitor.

   Do not coil the data cable. Shield the data cable with aluminum foil.

6. Driving a solenoid using the LabMaster
   The 9513 output current minimum is ±5 mA. The short circuit current is 40 mA. The maximum current may be 200 µA. You could contact AMD (Advanced Micro Devices) and ask them to fax you the relevant chapter. Alternatively, you could call Scientific Solutions (manufacturer of the LabMaster) and perhaps they could give you the specifications for the 9513.

   The Out 1 and 2 are intended to drive a logic level device. Driving a solenoid could put the 9513 out of commission.

7. Clampex acquires data, but Fetchex does not.
   When running pCLAMP 5 and pCLAMP 6 with the TL-1, Clampex does not use a DMA channel, but Fetchex requires a free DMA channel. A typical source of conflict is the original SoundBlaster sound card, which used DMA 1, same as the LabMaster board. If you have a sound card, remove it and see if that allows Fetchex to acquire data. In Fetchex ver. 6 you can also configure DMA 3; this requires you to re-set the DMA jumpers on the LabMaster motherboard (see the LabMaster diagram in this guide).

8. Error message: Waveform board not present
   Make sure that the correct version of Clampex 5 is being used. There are three versions. The TL-1 uses the CLAMPEXL.EXE and the Digidata 1200 uses CLAMPXDD.EXE.

9. Error message: Possible bad timer cable
   Try shielding the timer ribbon cable. Stretch the cable out and wrap it with a continuous sheet of aluminum foil from the point where the cable leaves the back of the computer to where it connects to the interface box. If this does not correct the problem, try swapping the motherboard with a motherboard from a working TL-1 system. If this fixes the problem, it appears to be a problem with the motherboard.

10. TL-1 is not responding to an external trigger pulse.
    A 5 V TTL pulse is needed to trigger the accept input. Please make sure that Do a Trial is selected and connect B2 to the interconnected Gates (1,2&3). When B2 is switched manually from Lo to Hi the acquisition should begin. If it does not, this may indicate that there is an problem with the TL-1. No connection needs to made to Out 2.

11. Testing TL-1
    If you have the pCLAMP 5 or pCLAMP 6 manual, then this should be sufficient for setting up the TL-1. Connecting Analog Out to Analog In with a BNC and running a protocol is one simple but effective test. You should be able to predict what you would expect to record from the scaling of the Analog Out and In. For instance, a 10 mV step from Analog Out scaled at 20 mV/V will deliver a 500 mV output. If the Analog In scaling is 100 mV/nA, then you should see a 5 nA signal displayed.

    Swapping components with a working TL-1 system is a straightforward method to test for failed parts. However, if either the motherboard or daughterboard of the TL-1 system has evidence of burned components or the computer in which the TL-1 was used underwent any sort of electrical damage, then you should not swap components.

    If you suddenly lose the analog output, the most likely cause is that the white DAC cable that connects to the motherboard at connector J1 (DMA system) or J4 (non-DMA system) has become dislodged. Although rare, it is possible that the ADDAC80 digital-to-analog converter chip on the LabMaster motherboard has failed. Use TEST-TL to determine if the other analog output (DAC 1) is operating properly. If so, you can swap the upper and lower DAC chips located at U3 and U4 on a LabMaster DMA motherboard (U34 and U35 on a non-DMA motherboard).

    You can calibrate your TL-1 analog output and input by adjusting 'trim pots' on the LabMaster motherboard and TL-1 daughterboard. Using the pCLAMP utility TEST-TL, a digital voltmeter and a small screwdriver, simply follow the procedure outlined below:

    1. Trimming procedure for the Analog Output
       1. Locate the trim potentiometers on your LabMaster. The potentiometers are located in the upper right-hand corner of the LabMaster DMA motherboard (upper left-hand corner of a non-DMA motherboard).
          
       2. Measure Analog Out 0 with a digital voltmeter.
          
       3. Run the TEST-TL utility and select the DAC (digital-to-analog converter) function. Choose Channel 0 and set the output voltage to 0 V. Adjust the offset potentiometer until the voltmeter reads 0 V. Potentiometer R7 provides the offset adjustment for DAC 0 on a LabMaster DMA motherboard (R5 on a non-DMA motherboard).
          
       4. In TEST-TL set the DAC 0 output voltage to 9.9 V. Adjust the gain potentiometer until the voltmeter reads 9.9 V. Potentiometer R5 provides the gain adjustment for DAC 0 on a LabMaster DMA motherboard (R3 on a non-DMA motherboard).
          
       5. Repeat steps 3 and 4 until adustment is no longer needed.

    2. Trimming procedure for the Analog Input
       1. First trim the analog output. Then connect DAC 0 directly to ADC 0.
          
       2. Locate the A/D gain and offset trim potentiometers. See the TL-1 Daughterboard diagram.
          
       3. Run TEST-TL and choose TrimMode. Set an output voltage of 0. Adjust the A/D offset trim pot until the screen reads 0.000 volts.
          
       4. Press to exit Trim mode, and choose TrimMode once again. Set the output voltage to 9.9 volts. Adjust the A/D gain trim pot until the screen reads 9.900 volts.
          
       5. Repeat steps 3 and 4 until adjustment is no longer needed.

 
 
Last Updated:  05 September 2004

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