Valeport MIDAS WLR User manual

© Valeport Limited
MIDAS WLR Hardware Manual Page 1 0730877D.doc
VALEPORT LIMITED
MIDAS WLR
Seabed Tide Recorder
Hardware Manual
Document Ref: 0730877
Document Version: D
Date: February 2007
This confidential document was prepared by the staff of Valeport Limited, the Company, and
is the property of the Company, which also owns the copyright therein. All rights conferred
by the law of the copyright and by virtue of international copyright conventions are reserved
to the Company. This document must not be copied, reprinted or reproduced in any material
form, either wholly or in part, and the contents of this document, and any method or
technique available therefrom, must not be disclosed to any other person whatsoever
without the prior written consent of the Company.
Valeport Limited, Tel: [phone]
St Peters Quay, Fax: [phone]
Totnes, e-mail: [email protected]
Devon, TQ9 5EW, Web: www.valeport.co.uk
UK
As part of our policy of continuous development, we reserve the right to alter, without prior
notice, all specifications, designs, prices and conditions of supply for all our equipment.
Copyright 2007

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CHAPTER DESCRIPTION PAGE
1INTRODUCTION...................................................................................................4
1.1 Contact Information ........................................................................................4
2SPECIFICATIONS ................................................................................................5
2.1 Sensor Specifications .....................................................................................5
2.2 Mechanical Specifications ..............................................................................6
2.3 Performance Specifications ............................................................................6
2.4 Sample Lifetime Calculations .........................................................................7
2.4.1 Based on Memory.....................................................................................7
A Note About Removable Memory....................................................................8
2.4.2 Based on Batteries ...................................................................................9
A Note About Rechargeable Cells ..................................................................10
3INSTALLATION...................................................................................................11
3.1 Communications With PC.............................................................................11
3.2 Deploying the MIDAS WLR............................................................................12
3.2.1 Real Time Operation...............................................................................12
3.2.2 Self Recording Operation .......................................................................12
3.2.3 LED Flashing Sequence .........................................................................12
3.3 Recovery ......................................................................................................13
4MAINTENANCE ..................................................................................................14
4.1 Changing Batteries .......................................................................................14
4.2 Seals.............................................................................................................16
4.2.1 O-Rings ..................................................................................................16
4.2.2 Anti-Extrusion Rings ...............................................................................17
5WIRING INFORMATION.....................................................................................18
5.1 Switch Plug...................................................................................................18
5.2 3m Y Lead (RS232) ......................................................................................18
5.3 3m Switched Y Lead (RS485 & RS422) .......................................................18

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1 INTRODUCTION
This manual covers the specification, wiring details and basic maintenance procedures
for the Valeport MIDAS WLR Seabed Tide Recorder. Full details of how to operate the
instrument with the DataLog Express software supplied are given in a separate manual.
As standard, the MIDAS WLR system consists of the following components:
•Titanium or acetal housed instrument
•Stainless steel deployment cage
•3m Y lead (interface to PC)
•Switching Plug
•Basic maintenance tools and spare o-rings
•DataLog Express Software CD
•Operating Manual
•Transit case
In addition, the following components may be supplied as optional extras:
•RS485 communications adaptor
•RS422 communications adaptor
•Bluetooth communications adaptor (19200 baud only)
•FSK modem communications adaptor (includes pcb in instrument)
•Various lengths & types of signal cable are also available
Note that instruments are often supplied (on request) with minor adjustments to the
above list, such as a 5m Y lead instead of a 3m Y lead for example. Such variations will
be detailed on the instrument packing list, and not in this manual.
1.1 CONTACT INFORMATION
If you have any questions about the operation of the instrument, which are not
answered by this manual, please contact your supplier if appropriate, or contact
Valeport Ltd directly at the address given at the front of this manual.

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2 SPECIFICATIONS
2.1 SENSOR SPECIFICATIONS
The unit is fitted with the following sensors:
Pressure
Type: Temperature Compensated Piezo-Resistive Sensor
Range: Various available, 10Bar (approx 100m water depth) to 600Bar
(approx 6000m water depth)
Precision: ±0.01% Full scale (±1cm for 10Bar sensor, ±0.6m for 600Bar)
Resolution: 0.001% Full scale (1mm for 10Bar sensor, 6cm for 600Bar)
Temperature
Type: Fast response PRT
Range: -5 to +35°C
Accuracy: ±0.005°C
Resolution: 0.001°C

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2.2 MECHANICAL SPECIFICATIONS
Materials
Housing: Titanium or acetal, as ordered
Exceptions: Temperature sensor is titanium.
Cage: Stainless steel (316 grade) with polypropylene clamping brackets
Dimensions: Instrument - 88mm Ø, 550mm long (including connector)
Cage – 750mm long x 140mm x 120mm
Weight (in cage): 11.5kg (air), 8.5kg (water).
Depth Rating: Acetal 500m (unless smaller pressure sensor fitted)
Titanium 6000m (unless smaller pressure sensor fitted)
Connectors
Instrument: 10 pin female Subconn bulkhead type (MCBH10F) with lock ring.
Comms Cable: Valeport 3m Y lead. 10 pin male Subconn line type (MCIL10M) to
instrument, 2 x 4mm bunch pins to external power, 9 pin female D
type to PC.
Switching Plug: 10 pin male Subconn line type (MCIL10M), with lock ring. Note
that the switch cap contains wiring links to activate the instrument
It is not a dummy plug.
2.3 PERFORMANCE SPECIFICATIONS
Memory: 16Mb solid state memory (upgradeable in 16Mb steps to 64Mb)
Internal Power: 8 x 1.5v alkaline C cells. The unit will accept 8 x 3.6v Lithium C
cells with no alterations required. Do not mix battery types.
External Power: Between 9 and 30v DC.
Current Drain: 25mA at 12v when running, and 0.25mA when in sleep mode.
Sampling Rate: 1, 2, 4 or 8Hz (synchronised)
Data Output: RS232, RS485 or RS422, depending on pin selection. Baud rate
is user selectable from 2400 to 460800

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2.4 SAMPLE LIFETIME CALCULATIONS
2.4.1 BASED ON MEMORY
Lifetime based on memory is simple to calculate. Pressure values use 4 bytes of
memory per sample, and temperature uses 2 bytes. Therefore total memory used per
record is 4 + 2 = 6 bytes.
The 16 Mbyte memory actually contains 16,777,216 bytes. Allowing a small amount of
memory usage for header files, the memory will store over 2.7 million records.
The length of time that this memory will last for obviously depends on sampling
scenario. Here are two examples:
Continuous data sampling, 8Hz:
Memory used per second is 8 x 6 bytes = 48 bytes.
Total memory fitted is 16,777,216 bytes.
Seconds before memory full is 16,777,216 / 48 = (approx) 349,500 seconds.
This is equivalent to 97 hours.
This period could be doubled by sampling at 4Hz.
Burst sampling, 4Hz, sampling 1 minute in every 10, recording all data points:
Memory used per burst is 6 bytes x 4Hz x 60 seconds = 1440 bytes.
The memory will therefore be full after 16,777,216 / 1440 bursts = 11650 bursts.
At a 10 minute cycle time, this is 116500 minutes, which is equivalent to 80 days.
Burst sampling, 4Hz, sampling 1 minute in every 10, recording averaged data:
Memory used per burst is 6 bytes.
The memory will therefore be full after 16,777,216 / 6 bursts = 11650 bursts.
At a 10 minute cycle time, this is 2796202 minutes, which is equivalent to 1941 days.

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A NOTE ABOUT REMOVABLE MEMORY
We are sometimes asked whether we offer these devices with removable memory. The
answer is no we don’t, but there are sound reasons for this. It is natural to think that
since removable memory cards are now the norm in consumer electronics, they must
be “state of the art” and therefore desirable in all applications, but this is not necessarily
the case.
•An essential feature of an underwater instrument is that it is water-tight; this is
achieved by using various seals on the mechanical parts of the device. Every
time that one of these seals is broken and remade, it introduces a small risk that
the seal is not correctly made, and the instrument could leak. The fewer times
that the device has to be opened, the better – you certainly wouldn’t want to do it
after every profile to get the memory card out.
•All memory cards are susceptible to ESD shock (static electricity) while being
handled. We take the view that the value of your data means it shouldn’t be
exposed to the possibility of this risk, which could result in loss of all data on the
card.
•Memory cards are not particularly efficient at storing data – they will only accept
minimum sized lumps of data at a time. This may be perfect for a camera where
you instantly generate a few Mbytes, not so for an application where you only
want to store a few bytes of data at a time.
•From a practical point of view, the time taken to connect a cable and extract the
data to PC is actually typically much less than the time to open the device,
remove the memory, replace the memory, and close the device up again.
•The implementation of removable memory is not technically difficult, but we
believe that the disadvantages currently outweigh any possible advantages in
this product and its applications. However, should circumstances change it will
of course be considered for future product enhancements.

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2.4.2 BASED ON BATTERIES
The MIDAS WLR will function with a voltage supply of between 9 and 30vDC. The
voltage output of the 8 x C cell battery pack will vary according to the type of cell fitted.
The most likely cells to be used will be standard alkaline type (1.5v each) or Lithium
cells (3.6v each), giving a 12v nominal output for alkaline cells, or 28.8v nominal for
Lithium cells. The following calculations are based on the same sampling scenarios as
the memory calculations, using figures for a 12v alkaline battery pack. Each example
also gives a figure for a Lithium battery pack, calculated from a basic ratio of alkaline to
Lithium performance.
In all examples, it is taken that an 8 C cell alkaline battery pack will have a nominal
capacity of 7.8Ah, and will be 75% efficient (total available charge, 5.85Ah), and that an
8 C cell Lithium pack will have a nominal capacity of 7.2Ah, and will be 95% efficient
(total available charge, 6.8Ah).
Continuous data sampling, 8Hz:
At 12v, the instrument draws 25mA when sampling.
Total charge available is 5850mAh.
Number of hours available is therefore 5850mAh / 25mA = 234 hours.
This is equivalent to just less than 10 days.
For Lithium cells, a similar calculation gives around 23 days.
Burst sampling, 4Hz, sampling for 1 minute every 10 minutes:
At 12v, instrument draws 25mA when sampling, plus 21mA for 5 seconds at the
start of each burst. It draws 0.04mA when in sleep mode between bursts.
In this scenario then, the instrument will draw 25mA for 60 seconds, then 21mA for
5 seconds , and then 0.04mA for 535 seconds. On average, it will draw:
Total charge available is 5850mAh.
Number of hours available is therefore 5850mAh / 2.71mA = 2158 hours.
This is equivalent to approx 90 days.
For Lithium cells, a similar calculation gives approx 215 days.
The above examples are intended as guides only. Valeport accepts no
responsibility for variation in actual performance. Note that performance of
individual battery cells is not always consistent.
(25 x 60) + (21 x 5) + (0.04 x 535)
= 2.71mA
(60 + 5 + 535)

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A NOTE ABOUT RECHARGEABLE CELLS
We are often asked if rechargeable cells can be used. Yes, it is possible to use
rechargeable cells, but we do not recommend it:
•Firstly, the cells cannot be recharged in-situ due to the possibility of the cells
giving out gas inside a sealed instrument, effectively turning it into an explosive
device. Whilst this risk is small, it does exist and therefore must be considered.
The risk could be overcome by adding an air vent to the housing, but this could
compromise the water-tight nature of the housing. Better to remove the risk
altogether.
•Secondly, the most commonly used rechargeable cells are NiCad type. These
only operate at around 1.2v maximum and have about 25% of the capacity of an
alkaline cell; they therefore give greatly reduced operating times.
•Modern Li-ion or NiMH cells are more efficient than NiCad cells, but do not yet
compare with alkaline cells. They are also considerably more expensive.