ING science detectors micrometers study for replacement.

Transcription

1 ING science detectors micrometers study for replacement. DOCUMENT CONTENTS Introduction What we have at the moment Advantages and disadvantages New device requirements Device search process and availability Digital option Analogue option Model selected and quotation Prototype work Micrometer installation geometry Necessary modifications Modifying the micrometer Modifying the cryostat holding plate Cost study and conclusion Introduction The aim of this small project is trying to improve the positioning measurement system for all existing CCD cameras in each of the science instruments, both the INT and WHT telescopes. At present there is an small but significant long standing problem with the existing system mainly related to the difficulty of making an accurate reading of the micrometer due to its small size, in addition to that the current system requires a high level of interaction not only for measurement but also to ensure that micrometers does not collide with the base where the cryostat is fixed when moving capstans hence displacing micrometer from holding position and finally we should make sure that the micrometer is not making contact with the base plate because the camera needs to be electrically isolated (floating ground). The present report is intended provide a definitive solution to the problem at a reasonable price and manpower to carry out all modifications required. In order to find the suitable item a meticulous search was necessary not only by visiting thousands of metrology related websites but also by sending tens of mails (containing

2 specifications for the item required) to companies which most likely have the product; I must said that with a little of success due to the special requirements for our applications. The more I search, the more interesting things I keep finding but the solution finally adopted on the conclusions of this document from my judgement I think that is more than good to allow for this study to conclude. WHAT WE HAVE AT THE MOMENT EXISTING MICROMETER STANDARD ARRANGEMENT At the moment we are using in all our cryostats the following micrometers: MITUTOYO Small Size " REF.: (spherical surface) MITUTOYO Small Size REF.: (flat surface) SPECIFICATIONS: RANGE: 6.5mm, GRADUATION: 0.01mm, ACCURACY: mm

3 DATASHEET: ADVANTAGES: Small size, easy to put in places where there is lack of space as is in this case. DISADVANTAGES: Difficult to read There is a need to make sure that the micrometer is not touching the plate either when adjusting the cryostat position moving the capstan also in normal operation after finishing CCD focusing operation.

4 Here is an example of a picture taken on august 28 th 2012 for a cryostat mounted at ISIS; as you can see the arrow is indicating the long standing issue of a micrometer being pushed back from its clamp position hence producing wrong readings:

5 (A more close view of the problem) NEW DEVICE REQUIREMENTS: SMALL SIZE EASY TO READ NO PHICICAL INTERACTION WITH THE MICROMETER REAL TIEME MEASUREMENT AS WE MOVE THE CAPTANS Ideally should be no need to perform any mechanical modifications in order to fit the new micrometers. SUFICIENT MEASURING RANGE ( > 3,0mm) AFFORDABLE PRICE

6 NEW DEVICE SEARCHING PROCESS AND AVAILABILITY General View of the market availability: Here are some of the links (in between thousands related websites visited) for the main micrometers makers and sellers companies which has interesting products: BROWN & SHARPE: PIEZO NANO POSITIONING: MITUTOYO: Heads C1544.aspx STARRETT: products/precision measuringtools/micrometers products/precision measuring tools/micrometers/micrometer Heads#itemsPerPage=24&currentPage=4&displayMode=grid&sortBy=none/asc TESA (Spain) MINI DIAL DEPTH GAUGE: a=x&ei=0spkubaolebe7abbn4fg&ved=0cc0qsaq&biw=1440&bih=741 BAXLO PRECISION: Reloj Comparador Digital Ref. CDM, Reloj Comparador CM/1

7 ALTECHNA: +High Resoliution+Micrometers STANDA: rometers PRECISION GRAPHIC INSTRUMENTS: BUY GAGE: Mini Mic Outside Micrometer.html MORE AND WRIGHT: and wright.com/products/show/4358?lang=english MADE IN CHINA: in china.com/product/wekntaychbub/china Dial Depth Gauge 5328.html STANDALT: For start, the new micrometer search was mainly focused on small size digital option (similar dimensions that the ones in use at the moment) but nothing was found; instead I found some with bigger dimensions but expensive.

8 DIGIGAL OPTION After analyzing a vast variety of digital micrometers here is the best option that I ve found and is possible to accommodate in the space available except the height, if deciding to use this device in some cases one data cable connector is needed to move to a different location:

9 Here is the quotation for one unit of the previous digital model: The digital option I do not recommend due to the size and price. LINEAR GAGES: SERIES 575 with Continuous Position Tracking Dimensions Note 1: 25mm and 50mm LGD Linear Gages have a stem of ø15mm (Tol. +0/-0.018). The LGD is Mitutoyo's new, ultra-compact ABS Linear Gage designed to fit into very tight spaces. It keeps track of its origin point once set. An EC Counter must also be ordered pdf

10 MORE DIGITAL OPTIONS: LVDT Hand-Tools/Gage-Amplifiers-and-Testers/Gage-Amplifier-Accessories/715-7 Dismissed due to the level of complexity for the application we need, but very interesting in case that useful direct reading from computer. sensors lvdt.htm ANALOG OPTION: In view of the existence of compact easy to read analog micrometers this alternative was also investigated but none met the maximum dimensions for space available to install them. Several mails to various leading companies in measuring instrumentation were sent but none gave an enthusiastic response mainly because they did not have anything in their catalogs that suited the requested requirements. In view of the lack of response from the major companies began searching the internet trying at all times to restrict increasingly the product I was looking for until finally and after examining several thousand links found a company with a line of compact indicators that was exactly what I needed.

11 Also found that a good option could be a compact back plunged indicators : Here are some of the links related to these items: a=x&ei=iektuajkb4mphafovydocw&ved=0cdyqsaq&biw=1280&bih=892#imgrc=_ =892&q=back+plunger+type+digital+indicators&oq=back+plunger+type+digital+indicat ors&gs_l=img ac.1.15.img.z4wlhpw-yku BEST ANALOG OPTIONS: EKSMA: This company has a vast variety of product, from optical components, opt mechanic and all sort of metrology devices. TRESNA:

12

13 MODEL SELECTED AND QUOTATION: I ve chosen the smaller analogue dial indicator micrometer that I could find, here is the specification sheet:

14

15 CONTACT POINT EXTENSIONS

16

17 (Chosen insulating ceramic contact as shown on this picture) Quotation for the chosen analogue device: No of Customer Your Ref Mr. José Norberto González Your letter Your VAT reg. no. Supplier/Customer Contact person Kerstin Lebeault Tel / Fax / kerstin.lebeault@kaefer-messuhren.de Your inquiry by dated We thank you for your request and submit the following quotation: Item Product Qty Price/Unit Dial Gauge MU 28 1 pcs 68,85 As we can see looks like a reasonable price.

18 PROTOTYPE WORK: Carefully checks have been carried out at the detectors workshop focused in finding the better options and the better way to install the new devices with the minimum amount of modifications. Cryostat inside view without electronic and or chip.

19 Cryostat inside view for the chip, electronic and connectors arrangement; as we can see there are normally minimum two extra spare holes to move the connectors if needed.

20 MICROMETERS INSTALLATION GEOMETRY: MINIMUN distance between the micrometer centre and the edge of the capstan is 15mm. MINIMUN distance between the micrometer centre and the cryostat body is 15mm.

21 Holding plate thickness is 10mm

22 Of course, we don t have 5mm range with the micrometers being used at the moment because we have to account for a reasonable separation to take in account possible tilt and electrical insulation; 1.5mm seems a reasonable figure. So in reality the present micrometers have 3.5mm measuring range. There are some limitations in the micrometer height due to the fact that unfortunately in a few cases micrometer location is right below to an electronic connector, as shown on this picture below:

23 DEVICE MODIFICATIONS STUDY NECESSARY MODIFICATIONS: In a few cases unfortunately micrometer location is right below a cryostat external connector leaving a mere 30mm free space to fit the micrometer. Due to the fact that is not possible to find either digital or analogue device small enough to in height for that tinny space in became necessary in those cases to move the mentioned cable connector to one of the other two spare connector holes available: (Only one of the two is necessary to move nor both) In those particular cases (micrometer right below cable connector) is possible to continue using the present type until the work for opening the cryostat can be carried out but still is possible to implement the new micrometer at the other two of the three positions. Due to the fact that 99.9% of the available micrometers in the market (either digital or analogue) have 8mm holding stem we have two options: Modify micrometer stem Modify the micrometer holes at cryostat holding plate

24 MODIFYING MICROMETER STEM: This option is possible, either in house modification o directly at the factory floor; I ve contacted to the selected micrometer supplier and they are ready to do the work for us and send me a quotation. In case that we decide to implement this modification on the micrometer I do recommend the factory option instead of modifying the device ourselves. In house modification of the micrometer have been considered and the work have been carried out successfully by our mechanical workshop but decided that is best if the necessary modification will be carried out by the device maker in order to preserve the necessary guarantee to cover any possible contingency that could arise.

25 Micrometer modified to allow fitting at the existing micrometers holes on the cryostat support plate. FACTORY MACHINED MICROMETER INSERTED AT THE CRYOSTAT HOLDING PLATE

26 QUOTATION:

27

28 MODIFYING CRYOSTAT HOLDING PLATE: If we ought to replace the existing micrometers there is no reason for keeping the compatibility with the existing stuff; from my point of view it is better to move in one direction. So we should modify the holding plate not the new micrometer, in between other reasons it is much more easy and cheap to modify the holding plate also a thinner micrometer stem can affect to it s performance. CRYOSTAT HOLDING PLATE (view from inside)

29 CRYOSTAT HOLDING PLATE (exterior view)

30 CRYOSTAT HOLDING PLATE MACHININING DETAILS (no micrometer modification needed)

31 MACHINED CRYOSTAT HOLDING PLATE TO ALLOW MICROMETER INSTALLATION AS IT COMES FROM THE FACTORY

32 CONCLUSIONS AND COST STUDY: Micrometer digital option had been dismissed for several reasons: High price Did not look to me good idea to attach any electrical device to the cryostat that could interfere and affect the science CCD performance (the chance is low but better not take any risk). The digital display micrometers bear as well a maintenance issue. Regular replacement of the battery will be forgotten and eventually astronomers will not be able to take readings to check the adjustments made. A suitable micrometer had been found that meets most of the initial requirements, KAIFER Small Dial Gauge Model MU28 (see all details above on selected model ): SMALL SIZE EASY TO READ NO PHICICAL INTERACTION WITH THE MICROMETER REAL TIEME MEASUREMENT AS WE MOVE THE CAPTANS SUFICIENT MEASURING RANGE ( > 3,0mm) AFFORDABLE PRICE PRICE PER UNIT: Small Dial Gauge Model MU /each plus shipping expenses Ceramic contact point as detailed in the quotation above 373/12 34,35 /each Some modifications are necessary to be able to fit the new selected micrometer (nothing is for free), we can choose between modify the micrometer itself or modify the cryostat holding plate also it is necessary to move a cable connector: MICROMETER MODIFICATION: It can be done at the factory floor and it costs 11,20 /each CRYOSTAT HOLDING PLATE MODIFICATION: In can be done at our own facilities at the cost of mechanical workshop manpower (about two hours per cryostat plate) plus detectors workshop manpower in order to remove the mentioned plate from the cryostat and place it back again (the amount of time required for this job still to determine and numbers should came out from the detectors section). I suggest having unless one base plate already modified in case that we have to open a cryostat anyway for other good reasons; this is not often the case.

33 MOVE THE CABLE CONECTOR: In some cases a cryostat cable connector became necessary to move to a different port as explained at the necessary modifications section. The possibility and time scale to carry out this job is up to the detectors department to decide and in principle it should cost no money but a few hours of the detectors specialist. This is how the new installed micrometer should look when the job is completed: View of the installed micrometer, ready for test on the telescope. The proper sequence and time scale for the new system implementation isn t a subject for this report, please do not hesitate to ask for further help if you think that is necessary. José Norberto Gonzalez Afonso