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  1. #71
    Administrator Forum Admin
    Join Date
    Oct 2000


    Here is my most recent test data in Walls survey program. As you can see, the closure error is fairly small, in fact it is closer that I got using a fiberglass tape, and Suunto survey compass. The test Jason and I did was when we were just starting with the MNemo, and didn't know how to calibrate the compass, or how to account for measuring around tie-offs, and knots.

    Click image for larger version

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    Last edited by FW; 04-23-2017 at 07:44 AM. Reason: typo
    Forrest Wilson (with 2 Rs)
    Any opinions are personal.
    Sump Divers

  2. #72


    Another update:

    I just tried the Mnemo underwater again, this time for a section of unknotted line laid by someone who has already been reminded numerous times of the magnitude of his crime. Since then the system has reversed and there was a lot of debris on the line. I was using the device in Basic mode, which is very easy.

    The first few shots went fine, but after 4-5 shots I found that the display was not flashing as I moved the Mnemo up the line. I am pretty sure that this was because debris on the line had jammed the wheel. I had tried to clean off the line with my fingers as well as I could before it went through the Mnemo, but inevitably some got in there.

    When I got home I flushed clean water through and it started working fine again.

    I think there are unfortunately still situations where a compass and tape are the best option.


  3. #73


    Here are some tips and tricks related to the different issues/questions that appeared during tests and review :

    -Wheel jamming:

    This of course always a possibility with old/dirty line and the main contributing factor will be the lack or little tension of that line . When that happens a trick that worked fine for me ( only happened once to myself ), is to hold the line in a hand, increase the tension and then swiftly roll back and forth the mnemo to clean the wheel, that should do the trick probably in 90% of the cases. Of course after that you?ll have to resurvey that particular shot. If you notice the wheel is not spinning first check if the line has enough tension and if possible adding an extra wrap on a tie off to increase the tension often solves the problem.

    -Concerning calibration :

    Ignore the number after the message displayed, when you are asked to place the device on each side, randomly go from one side to the other making sure it lays at least 5s on each side. Move slowly from one side to the other. Repeat that until the screen turn green indicating the end of calibration.

    -Obstacles on the line:

    It is important to know that the device measures distance whether you move it forward or backward. This is done intentionally. In case you have an obstacle on the line (thick knot, arrow etc .. ) , roll the mnemo all the way to the obstacle, then back the length of the obstacle plus the size of the Mnemo. Unclip it from the line (do not stop the survey or add a station) and clip it on again after the obstacle. Resume rolling the device until you reached next station.
    Like this no loss of time to rearrange the line.

    -Compensation for thick tie wraps:
    You can compensate the loss in measurement of the round part of a large tie wrap by rolling back the device the estimated distance that is missing.

    -Display or not display :
    We recommend all user of Mnemo to get familiar enough with the device to use only the colors of the screen and not read the menu at each station. This will increase the smoothness of the process and allows them to focus on stabilizing and clipping on and off the device. A special mode (called BASIC) for very bad visibility and deep diving will be introduced shortly. This will use only color code during survey.

    -Opening the pressure plate (gate)
    Brute force WON?T help. Hold the white lever between thumb and index, apply a rotational force forward and THEN pull backward. Although the actual configuration is hard to operate it is also the one that offers, in my opinion the safest grip on the line. Futur devices will have the option to replace the central hard spring by two softer ones on each side.

    -Organizing work, multiple sections

    I personally call all my section AA1 ? In most cases I can remember what I survey and in which order. In more complex scenario you can either take the time to change the name of the section or write on an slate complementary information.

    Hope some of this was can be of help.


  4. #74
    Administrator Forum Admin
    Join Date
    Oct 2000


    Thanks Sebastian.

    Forrest Wilson (with 2 Rs)
    Any opinions are personal.
    Sump Divers


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