ALMA Phasing Project H Maser Procedures ALMA
Contents
1. Chapter 2 Network Access This section itemizes the various ways the Maser appears on the network 2 1 Network Commanding The H Maser currently deployed at the AOS at IP address 10 197 48 50 If it needs to be re deployed at a new address follow RD3 to change its internal configuration and redeploy the MASER in the TMCDB 2 2 Network Commanding For monitor and control through the network interface the Maser speaks UDP at port 14000 From linux machines it is convenient to use netcat see the man page for nc 1 but there are also linux mac applications that can equivalently be used to perform the task The commands are documented in RD2 To verify connectivity you can use the GETID command aos gns gt nc u p 14000 10 197 48 50 14000 GETID GETID Hard T4S 711 0ct12 b 37 Soft T4S SW 100 a 15 Generally the commands are echoed CommandName and the response to the command if the comand is understood and CommandName if not e g html 1 html 1 blahblah 43 blahblah 43 2 3 Web Monitoring The maser has an internal web server to provide its current housekeeping This is available at 10 197 48 50 80 on the AOS network 2 4 ALMA Monitoring The Maser software Device RD4 provides all of the above housekeeping at similar cadence to the normal monitoring system as configured in TMCDB It is supported in R2014 2 and may be backported to other releases When it is in use H Maser d2. Atacama Large Millimeter submillimeter Array ATACAMA LARGE MILLIMETER ARRAY ALMA Phasing Project H Maser Procedures ALMA 05 11 21 02 0001 A PRO 2013 08 14 Prepared by Organization Role Date and Signature G Crew MIT Approved by Organization Role Date and Signature Authorized by Organization Role Date and Signature Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 2 of 18 ALMA Phasing Project H Maser Procedures Change Record Version Date Affected Section s Author Reason Comments A 2013 08 14 All G Crew First Issue 2014 09 24 5 G Crew Added Safety Section 2014 10 03 2 G Crew minor edits 2014 10 03 6 G Crew Added Software Section Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 3 of 18 ALMA Phasing Project H Maser Procedures Contents Change Record 2 1 Introduction 5 Li PUEDO oca a a a AA a Ge 5 LE ADE teaa a a DA AAA 5 1 3 Reference Documents uo ocas 22 6b dR rea aaa 5 IA A ci ee eS ras EE RRO EE RRA TARA de 5 2 Network Access 6 21 Nemo ConmandiE ee Lk be ee nae eee oe ee a a E A 6 22 Webwork Commanding ss lt s s NE EA a ee a ae a 6 29 Wob MIG s er ras ginan AAA AR A AA 6 2 ALNA Diba ccoo rra A a ee 6 Be A A APRS aw ES Ob ee Aa de ae 7 3 Network Shutdown and Restart Procedures 9 3 1 Remote Shutdown Procedure 9 3 2 Remote Restart Procedure a c c
3. Chapter 1 Introduction 1 1 Purpose The H Maser provided to ALMA by APP comes with extensive documentation and is designed to run unattended It is also under a support contract from T4Science http www t4science com This document is intended to gather all maintenance or other procedures in one place for convenience 1 2 Scope This document is limited to certain essential procedures and assumes access to the underlying reference documents for full particulars 1 3 Reference Documents The following documents contain additional information are referenced in this document and should be consulted for further more detailed information Table 1 1 Reference Documents Reference Document Title Document ID RD1 Installation_Operation_and_Maintenance_ User_manual_iMaser_T4S MAN 0012_1_7emc 2 pdf RD2 T4S MAN 0015v1 3_Network_Monit_User_Manuel al4 Option RE DIST pdf RD3 T4S PROC0011_IP_address_change_ IO_card_general pdf RD4 APP Update to Corr Control Design ALMA 05 11 61 01 0001 A DSN RD5 Installation of interrack cables and switchover procedure Hydrogen Maser Frequency Standard for the CLOA ALMA Phasing Project 1 4 Acronyms ALMA Atacama Large Millimeter submillimeter Array APP ALMA Phasing Project MIT Massachusetts Institute of Technology ALMA 05 11 21 02 0002 A PRO Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 6 of 18 ALMA Phasing Project H Maser Procedures
4. Section 7 1 Switch on the HF receiver HF revr switch 2 Switch on the Beam stabilizer Beam stab switch 3 Wait for Ipur and Meas H to stabilize and be close to their previous operation conditions This usually takes about 15 min 4 Switch on the RF oscillator HF generator RF osc switch 3 5 Switch to Rb Maser Full particulars may be found in RD5 Section 9 Briefly e Disconnect the H Maser 10 MHz cable e Connect the CVRR1 internal cable to the splitter e Disconnect the H Maser 5 MHz cable e Connect the Rb Maser 5 MHz cable e Verify proper operation of the system e Leave the H Maser on 3 6 Switch to H Maser Full particulars may be found in RD5 Section 7 Briefly e Disconnect the Rb Maser 5 MHz cable e Connect the H Maser 5 MHz cable e Disconnect the CVRR1 internal cable from the splitter e Connect the H Maser 10 MHz cable e Verify proper operation of the system e Leave the Rb Maser on Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 11 of 18 ALMA Phasing Project H Maser Procedures Chapter 4 Monitoring Procedures 4 1 Routine Monitoring Primary The primary indicator of Maser health for ALMA is to review the maser counter datum MASER_VS_GPS_COUNTER under the AOS CONTROL_AOSTiming_CRD on http monitordata osf alma cl As with the Rb Maser there is a counter that counts the number of 125 MHz cycles per GPS tick The Rb Mas
5. 10 197 48 197 10 197 48 197 220 ts FTP server Version 6 00LS ready Name 10 197 48 197 gcrew ftp 331 Guest login ok send your email address as password Password ftp 230 Guest login ok access restrictions apply Remote system type is UNIX Using binary mode to transfer files ftp gt cd printfiles 250 CWD command successful ftp gt dir ftp gt mget Note that the directory only holds 15 files 0 14 and then they overwrite 4 4 Optional Monitoring Frequency Counter An interval counter has been temporarily deployed to monitor the Maser tick relative to the GPS tick This device was deployed at 10 197 60 66 and is accessible at port 5024 The following script may be run to capture the offset between the Maser and the instantaneous GPS tick Note that over the course of a day the GPS tick will wander by some 30 ns due to diurnal ionospheric variations of total electon content import telnetlib time Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 13 of 18 ALMA Phasing Project H Maser Procedures host 10 197 60 66 port 5024 tn telnetlib Telnet host port tn read_until A gt set to start from known state tn write b RST n tn read_until A gt set a 5s measurement timeout tn write b SYST TIM 5 0 n tn read_until A gt configure 2 ch measurement tn write b CONF TINT 01 2 n tn read_until A gt set AC coupling for both channels tn
6. 14 17 24 715304 most recent archival files 08 05 14 04 51 2000081 08 05 14 04 51 1876731 08 05 14 04 51 1881079 MonitInst dat MonitMax dat MonitMin dat MonitInst_05082014_04_51 MonitMax_05082014_04_51 MonitMin_05082014_04_51 The mget command is convenient for retrieving everything which can then be tar d and deliv ered to T4Science for their analysis The Maser automatically reopens new files every 2 MB or so The current files have no time tag in the name Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 9 of 18 ALMA Phasing Project H Maser Procedures Chapter 3 Network Shutdown and Restart Procedures This section covers issues related to power outages The Maser is on the AOS backup power supply system so no action is required on short outages Moreover it has internal UPS batteries which are rated for 30 hours of operation In the case of a prolonged outage it can be placed in a standby power mode which draws less power This allows the maser to return to service immediately after a prolonged outage perhaps 2 days If the outage is longer that that the Maser will shut down and will require a longer restart period During this time the Rb Maser should be used for ALMA operations Sections 8 and 9 of RD1 refer to buttons that existed textitbefore the network monitor and control upgrade was made The functions of those buttons are now available only via the network as document
7. 001 A PRO Date 2013 08 14 Page 18 of 18 ALMA Phasing Project H Maser Procedures GET_HLight GET_ITHeater GET_IBHeater GET_ISHeater GET_UTCHeater GET_ESHeater GET_EBHeater GET_IHeater GET_THeater GET_BoxesTemp GET_IBoxes GET_AmbTemp O GET_CField GET_UVaractor GET_UHTExt GET_IHTExt GET_UHTInt GET_IHTInt GET_HStPres GET_HStHeat GET_PiraniHeat GET_U405kHz GET_UOCXO GET_P24VDCO GET_P15VDC GET_M15VDC GET_P5VDC GET_M5VDC GET_P8VDC O GET_P18VDC GET_Lock GET_DDS O Note that the housekeeping is only updated to this interface every few minutes so reads at a higher data rate will not return higher sampling
8. 31T12 10 52 1406808653 0 4 33144699058050E 007 2014 07 31T12 10 53 1406808654 0 4 33169113120550E 007 2014 07 31T12 10 54 1406808655 0 4 33090988120550E 007 2014 07 31T12 10 55 1406808656 0 4 33188644370550E 007 2014 07 31T12 10 56 1406808657 0 4 33169113120550E 007 showing a 433 ns separation between the two ticks Note that the maser tick is not used for anything so the important point here is that the output be slowly varying The GPS PPS tick and can be adjusted using the remote monitor and command interface as described in RD2 That same interface can also be used to adjust the maser frequency Generally speaking there should be no need to do either For example aos gns gt nc u p 14000 10 197 48 50 14000 adjust the PPS nanoseconds RDREG ADJ1PPS RDREG ADJ1PPS 337498120 ADJ1PPS 337497800 RDREG ADJ1PPS RDREG ADJ1PPS 337497800 adjust the relative frequency synthesizer rate RDFS RDFS 1420405750 294396 SETFSREL 5 0e 14 SETFSREL 5 0e 14 RDFS RDFS 1420405750 294469 You should however consult RD2 for full details Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 15 of 18 ALMA Phasing Project H Maser Procedures Chapter 5 Safety Procedures Safety protocols associated with the APP Maser operation and maintenance are described in the following sections 5 1 Shipping If for any reason the maser should need to be removed from the ALMA LO s
9. ata is collected at http monitordata osf alma cl e g the data from July 12 2014 is to be found at http monitordata osf alma c1 index php dir 2014 2F07 2F2014 07 12 2FCONTROL_VLBI_Maser 2F Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 7 of 18 ALMA Phasing Project H Maser Procedures iMaser59 14 08 2014 17 34 06 MONITORING RECORD ON 300 sec U batt A V 27 661 EB heater V 12 715 Pirani heat V 12 115 I batt A A 0 837 I heater V 6 66 Unused 0 054 U batt B V 27 905 T heater V 8 247 U405kHz V 11 803 I batt B A 2 576 Boxes temp C 46 777 U OCXO V 4 16 Set HIV 5 38 I boxes A 0 585 24 VDC V 24 9 Meas HIV 1 288 Amb temp c 22 119 15 VDCIV 1469 puria 0 472 Cfieldivw 5 09 15VDC VI 15 665 I diss A 0 481 Uvaractor V 5 588 5 VDCIV 5 16 H light VI 2 897 UHText kv 3 502 S5VvDCIV o IT heater V 10 908 HT extluA 5 737 8 VDCIVIJ 809 IB heater V 8 384 UHTint kv 8 508 18 VDC V _ 17 34 ISheater V 0 054 IHT int ua 6 226 Unused 0 08 UTC heater V 14 18 Hst pres bar 1 143 Lock 1 ES heater V 11 836 H st heat V 14 874 DDS 1420405750 294469 Figure 2 1 Sample Maser web page The software device retrieves its data through the web interface and provides it to the monitoring system You can also retrieve the same data via the CCL interface import CCL Maser maser CCL Ma
10. current environmental protocols for proper disposal Dis posal protocols are subject to change but may potentially include a return for credit in order to reclaim reusable materials 5 4 Electronics Package The maser employs ESD sensitive electronic modules so appropriate precaution shall be taken if working with the cabinet door open The electronics package also supplies a high voltage source to the Physics Package which is adequately isolated from normal access to the cabinet as long as none of the internal wiring or components is disturbed 5 5 Physics Package and Hydrogen Source The Physics Package is a self contained subsystem within the maser which operates from a high voltage supply and employs internally a high vacuum pump and a hydrogen source addressed below This subsystem and the connections from the Electronics Package shall only be serviced by the manufacturer or their designated maintenance contractor The hydrogen source poses no threats to the user as long as it remains sealed in the physics package The solid compound from which the molecular hydrogen is liberated LaNi5H x only produces hydrogen in very small amounts as needed to maintain storage bulb pressure while the physics package is operating The MSDS for this material states that risk due to fire and explosion from this material is extremely weak Handling the source in raw or bulk form however poses a health risk Therefore no attempt should ever be made to acc
11. ed poorly in RD2 3 1 Remote Shutdown Procedure Switch off the Dissociator then switch off the Beam Stabilizer aos gns gt nc v u C 10 197 48 50 14000 DISSSW 0 BEAMSW 0 See Section 2 2 for more detail on the network commanding Note that if the maser is remotely shutdown it will need to be remotely restarted The remote commanding and physical switches must all be in a consistent state 3 2 Remote Restart Procedure Switch on the Beam Stabilizer aos gns gt nc v u C 10 197 48 50 14000 BEAMSW 1 and wait until the purifier current IPur and Hydrogen pressure Meas H are stable and close to their previous values This can take upwards of 15 minutes Then turn on the Dissociator aos gns gt nc v u C 10 197 48 50 14000 DISSSW 1 See Section 2 2 for more detail on the network commanding Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 10 of 18 ALMA Phasing Project H Maser Procedures 3 3 Manual Shutdown Procedure Full particulars are found in RD1 Section 9 1 Switch off the RF oscillator HF generator RF osc switch 2 Switch off the Beam stabilizer Beam stab switch 3 Switch off the HF receiver HF revr switch Note that if the maser is manually shutdown it will need to be manually restarted The remote commanding and physical switches must all be in a consistent state 3 4 Manual Restart Procedure Full particulars are found in RD1
12. er is conditioned by the GPS so with the Rb standard the datum should increase by 125000000 each second The Maser is NOT conditioned by GPS so it will in general increment by a similar number per second What that number is depends on how the Maser has been tuned Ideally and to avoid confusion it should be tuned so that the increment is exactly 125000000 per second In any case a systematic change of this expected behavior on any timescale is a problem 4 2 Routine Monitoring Secondary The monitor data captured at http monitordata osf alma cl for the maser should be reviewed for variations The CLOA room is temperature controlled to within a few degrees so the thermal sensors should not vary much but the heater voltages will in general vary to thermally stabilize the maser against external temperature variations The alarm page RD1 Section 12 identifies optimal values for all the parameters Items that are in the Orange or Red ranges should be referred to T4Science Haystack for consultation 4 3 Optional Monitoring Allan Variance An Allan variance monitoring device is currently on site with a good reference crystal It is deployed at IP address 10 197 48 197 There is a command to start the Allan variance monitoring and another to stop it You will need to restart it and return a few hours later aos gns gt nc p 1299 10 197 48 197 1299 Welcome to the Symmetricom 5115A 10 197 48 197 gt show screens if you re cu
13. ess or service the material directly Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 17 of 18 ALMA Phasing Project H Maser Procedures Chapter 6 Maser Software Device 6 1 Routine monitoring There is a software device for the maser which is used by the monitoring system to propagate housekeeping to the monitoring site http monitordata osf alma cl under CONTROL_VLBI_Maser whenever software release 2014 2 or later is run All the monitor points from the embedded Maser HTTP server are present with similar names 6 2 Maser CCL Commands Under release 2014 2 or later a set of CCL commands may be used to access the maser house keeping There is a top level status command aos gns gt ipython import CCL Maser maser CCL Maser Maser maser STATUS which prints the data in the canonical STATUS way In addition there is a pair of command to capture the data in the same format T4Science uses in the internal data monitoring maser getOneLineHeader maser getOneLineOfData Additionally a short report is also available this command exists to support a GUI panel that has yet to be created story isHealthy isLocked maser getMaserStatus 6 3 Maser CCL Monitor Points And finally all the monitor points are explicitly available GET_MaserTime GET_UBattA GET_IBattA GET_UBattB GET_IBattB GET_SetH GET_MeasHO GET_IPurO GET_IDiss Doc ALMA 05 11 21 02 0
14. osa ca s e eaa a s eoe ee ee aa Ea 9 3 0 Mamnal Shutdown Procedure lt ss 266 0204 022 22 we eae eee aR ew 10 oa Manual Restart Procedure lt s q e re t iaa a 0066 Soe oa ee a 10 3 6 Switch to Ro Maser 44 445045 40005 eA Ra Re RRR a 10 30 Peaster be H MESE comio a ew ee DOR ee ad 10 4 Monitoring Procedures 11 41 Routine Monitoring Pruviary inc sa a RR OER A oS 11 4 2 Routine Monitoring Secondary 0000 eee ee ee 11 4 3 Optional Monitoring Allan Variance e e 11 4 4 Optional Monitoring Frequency Counter o 12 5 Safety Procedures 15 ul UU a a e ee ee ek ee eR EEE ERRR EE See a ee ed 15 2 Installation and Handling o ep ke A ida ee RRR RR SESS 15 B S Batteries amd UPS 2 344 444466424 AAD asa 15 Ba Mletiromes Package oa bb we das A RA eK eS ew 16 5 5 Physics Package and Hydrogen Source 0 000000000004 16 6 Maser Software Device 17 e1 Je TOMO ae oe wed be ee a E A REDS A a ns 17 6 2 Maser UCL Commands o ida a ARR RRO EO RS 17 ALMA Phasing Project H Maser Procedures Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 4 of 18 6 3 List of Figures 21 Sample Maser web page List of Tables 1 1 Reference Documents Maser CCL Monitor Points ALMA Phasing Project H Maser Procedures Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 5 of 18
15. rious 10 197 48 197 gt print spectplot Printing to local file in ftp directory pub printfiles 10 197 48 197 gt print adevplot Printing to local file in ftp directory pub printfiles 10 197 48 197 gt print freq Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 12 of 18 ALMA Phasing Project H Maser Procedures Printing to local file in ftp directory pub printfiles 10 197 48 197 gt show adev you 1l see something like this TAUO 1E0 NEQ BW 0 5 Hz tau 1 adev 9 82e 14 err 8 70e 16 tau 2 adev 9 53e 14 err 1 19e 15 tau 4 adev 8 91e 14 err 1 58e 15 tau 10 adev 9 44e 14 err 2 64e 15 tau 20 adev 1 080e 13 err 4 28e 15 tau 40 adev 1 27e 13 err 7 10e 15 tau 100 adev 1 79e 13 err 1 58e 14 tau 200 adev 2 59e 13 err 3 23e 14 tau 400 adev 4 1e 13 err 7 20e 14 tau 1000 adev 7 6e 13 err 2 08e 13 tau 2000 adev 1 16e 12 err 4 32e 13 tau 4000 adev 2 2e 12 err 1 09e 12 and to start a new collection cycle 10 197 48 197 gt control take 10 197 48 197 gt stop 10 197 48 197 gt start gt 10 197 48 197 gt control yield If you take control you should yield it as soon as possible If your session times out for whatever reason you can be locked out of the box until a power cycle clears it To retrieve any files printed above you use ftp to the device aos gns gt ftp 10 197 48 197 Connected to
16. se the units cannot be resealed once opened The manufacturer provided MSDS shall be included in the site MSDS binder in closest proximity to the maser installation Even in a partially discharged state the batteries are a high current low voltage energy source They have no off switch and can produce burns to personnel if terminals are accidentally shorted Use of electrically insulated tools is recommended and only persons trained in UPS maintenance and handling of heavy batteries shall service the UPS The batteries weigh 19 kg each and this mass is concentrated in a small volume Therefore battery handling carries a risk of injury from dropping and current ALMA safety practices shall be observed with a minimum recommended PPE to include safety shoes eye protection gloves and material handling equipment especially if multiple units need to be handled simultaneously In normal operation the sealed units do not vent hydrogen gas In the case of a malfunction in the charging system hydrogen outgassing could occur APP recommends that ALMA operations Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 16 of 18 ALMA Phasing Project H Maser Procedures include periodic inspections of the charging system and assure the local ventilation is adequate for safe continued UPS operation Exhausted batteries shall not be disposed of by placing in dumpsters or other common trash receptacles but shall be handled under
17. ser Maser maser STATUS 25 FTP Data The maser provides an internal ftp site tp 10 197 48 50 which contains some configura tion files and internally collected monitor data Normally the monitoring data captured as described in the preceeding section 2 4 is adequate but in the event of some issue with the maser T4Science will probably want to see this data for detailed analysis aos gns gt ftp 10 197 48 50 Connected to 10 197 48 50 10 197 48 50 220 Service ready for new user Name 10 197 48 50 gcrew iMaser 331 User name okay need password Password ndcu 230 User logged in proceed Remote system type is Windows_CE ftp gt dir 227 Entering Passive Mode 10 197 48 50 192 2 125 Data connection already open transfer starting 01 06 14 16 34 lt DIR gt Embedded_soft 01 06 14 16 34 lt DIR gt Monitoring ALMA Phasing Project H Maser Procedures Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 8 of 18 The Embedded_soft directory contains command configuration files which may potentially be adjustable Do not change any of them without knowing what you are doing as that may break the maser or the monitoring system ftp gt cd Monitoring 250 Requested file action okay completed ftp gt dir 227 Entering Passive Mode 10 197 48 50 192 9 125 Data connection already open transfer starting current files 08 14 14 17 24 761077 08 14 14 17 24 714599 08 14
18. write b INP1 COUP AC n tn read_until A gt tn write b INP2 COUP AC n tn read_until A gt set input impedance to 1 Mohm tn write b INP1 IMP 1 0E6 n tn read_until A gt tn write b INP2 IMP 1 0E6 n tn read_until A gt set start threshold to 1V tn write b INP1 LEVi 1 0 n tn read_until A gt set stop threshold to 1V tn write b INP2 LEV1 1 0 n tn read_until A gt set start slope to positive rising CH1 tn write b INP1 SLOP POS n tn read_until A gt set stop slope to positive rising CH2 tn write b INP2 SLOP POS n tn read_until A gt hold off gate close tn write b SENS GATE STOP HOLD SOUR TIME n tn read_until A gt hold off for 200 ns tn write b SENS GATE STOP HOLD TIME 200E 9 n tn read_until A gt start meas when gate recd tn write b SENS GATE STAR SOUR IMM n tn read_until A gt stop meas when holdoff done tn write b SENS GATE STOP SOUR IMM n Doc ALMA 05 11 21 02 0001 A PRO Date 2013 08 14 Page 14 of 18 ALMA Phasing Project H Maser Procedures tn read_until A gt enable gate settings tn write b SENS TINT GATE SOUR ADV n for i in range 4320000 tn write b READ n tn read_until A gt s tn read_until r print time str time Y m dT H M S time gmtime time time s tn close Variations on this script are possible The output of the current script looks like 2014 07
19. ystem for shipment the hydrogen source may fall under special compliance for import and export protocols These are subject to change so the operations and maintenance staff should be keep current with changes in these protocols and prepared to meet current regulations 5 2 Installation and Handling If for any reason the maser should need to be removed from the ALMA LO system for service or shipment only personnel that have been previously trained in ALMA safety procedures and have experience with material handling shall be directly involved Personnel directly involved shall at a minimum employ PPE which includes eye protection gloves safety shoes and material handling equipment If the maser rack should be unfastened from the seismic support structure retain all mounting hardware required to re install the rack to preserve seismic compliance Some of the hardware subjected to high torque during installation may need to be replaced for reinstallation in order to comply with the seismic installation requirements Reinstallation shall only be executed by personnel acquainted with current seismic compliance requirements 5 3 Batteries and UPS The UPS batteries are of type Sonnenschein dryfit A500 A512 55A sealed lead acid main tenance free units with a gelatinous electrolyte and shall not be opened for any reason The electrolyte is corrosive and can cause skin burns therefore no attempts shall be made to replen ish the electrolyte becau
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