Transcript
50521 CONTINUOUS MONITORING SYSTEM
Operating Instructions 3651 Walnut Avenue, Chino, CA 91710 Phone: (909) 627-8178 Fax (909) 627-7449 www.descoemit.com
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50521 CONTINUOUS MONITORING SYSTEM Operating Instructions Introduction The Desco EMITs’ 50521 provides constant monitoring of personnel and work surface grounding using patented resistive loop technology. No other method is as direct and reliable. The 50521 is unaffected by capacitance variations associated with personnel and environmental conditions. 50521 Specifications • • • • • • •
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Monitors two operators and two ground connections (i.e. work surface) independently. Fully independent alarming conditions: audible and visual. One safe light for all four monitored points (operators and work surfaces). Two independent operator remotes with 10’ wires. SCCN compatible data output. Size: 4.7" W x 4" D x 1.4" H. Plug-in power supply: 110 VAC/60Hz input, 12VDC/500mA output or 230VAC/50Hz input, 12VDC/500mA output. 2.1mm connector – center negative. Any alternate transformer must comply with the Safety Extra Low Voltage (SELV) insulation requirements. Important: The earth connection on this unit is only used for operational purposes. It is considered to be class I and tested as class II. The power supply connection plug is accessible to the user and there is no safety insulation inside the 50521. Therefore the insulation of the power supply is critical. Rated Power consumption: 1.8VA
Environmental Conditions • • • •
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Suitable for indoor use only at altitudes not exceeding 6500ft. (2Km) Maximum relative humidity of 80% up to 88oF (31oC) decreasing linearly to 50% @104oF (40oC) Pollution degree 2 per IEC 644 Temperature range of 41oF (5oC) to 104oF (40oC)
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Installation This installation section is written to cover the 50521 as per Figure 1. A.
Determine the mounting location of the monitor. The unit can easily be mounted on top of the work surface or underneath a shelf using the Velcro strips provided. The front panel of the monitor should be visible to both of the operators.
B.
Determine the mounting locations of the operator remotes. The grey remote is for operator #1 and the black remote for operator #2. Make sure that each remote is located so that the remote leads reach the monitor.
C.
Attach the remotes to the bench or other surface using the screws provided.
D.
Attach the work surfaces to ground using the supplied ground cords. (See Figure 1). Tie the ring terminal end of the cord to the bench common ground point or other appropriate ground point. For safety, we strongly recommend that a 1M-Ohm resistor (not supplied) be fitted between each work surface and its ground point. Attach the larger, 10mm, snaps at the opposite ends of the cords to the snaps on the work surface snap plate.
WORK SURFACE 1
WORK SURFACE 2
TO COMMON POINT GND (NOT SHARED WITH ELECTRICAL GND POINT) WE RECOMMEND THAT 1Meg-Ohm RESISTORS BE FITTED IN SERIES FOR THE SAFETY OF OPERATORS.
Figure 1, Work Station Wiring Connections TB-6513
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E.
Attach the black ground wire from the monitor unit to an alternate ground point. It is important that this ground wire is attached to a different ground point than the work surface ground cords of the previous step to ensure proper, independent monitoring. The faceplate screw of a grounded AC wall outlet may provide a convenient connection point.
F.
Attach the monitor unit using the Velcro strips provided.
G.
Route the hardwired work surface ground monitor cords from the back of the monitor unit, to the 7mm snaps attached to the snap plates. Snap the grey work surface ground monitor cord to the snap plate of operator #1 and the black work surface ground monitor cord to the snap plate of operator #2. These ground monitor cords are used for sensing whether or not the unit is indeed grounded.
H.
Route the operator remote cords to the monitoring unit and insert the modular plugs from the remotes into the appropriate modular sockets on the rear of the unit. (See Figure 1)
I.
Plug the DC power supply plug into the power jack in the rear of the unit. Route the wire from the supply to a nearby AC outlet and plug the power supply into the outlet. The monitor is now powered.
Mat Grounding It is recommended to connect the mat wire (7mm snap) from the monitor and the mat ground wire (10mm snap) to two separate points on the bench mat as in Figure 2.
SE872
Ground Ref. Wire
NOTE: the upper limit (fail Hi) of the mat circuit is approximately 3.5M ohms. Taking into account the 1Mohm resistor in the mat ground wire, the resistance between the 7mm and 10mm snaps must be below 2.5M ohms. If the mat resistance is above this value, the two snaps must be physically connected by the supplied metal plate (SE95-2).
Figure 2, Mat Grounding
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Fitting Snap Plates to Bench Mats Fit the conductive plate to the mat with either the eyelets or threaded nuts and screws included in the kit. Fit the plate about 2.5cm (1”) from the corner of the mat as shown in Figure 3.
Approx. 1”
Approx. 1”
Bench Mat
10mm male snap
7mm snap socket
Conductive plate
For use with supplied screws
Bench mat
For use with stud tool (Not supplied)
Figure 3, Fitting Snap Plates To Bench Mats
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Fitting ground monitoring wires to Buried, Conductive Layer Benches First, countersink-drill the top dissipative layer to expose the conductive, buried layer then fit countersunk bolts, of sufficient length, to the bench after drilling completely through the bench top. Recommended bolts are M5 or ¼” – measure your bench top thickness to determine required length. Next, crimp or solder both the Ground and Monitor wires to separate ring terminals then fit these wires to the bolts as shown in Figure 5. Min. 1”
Min. 1”
Min. 1”
Bench Top
Figure 4, Countersunk Bolt Positioning
1 – Countersunk bolt 2 – Flat washer 3 – Ring terminal 4 – Star washer 5 – Nut 6 – Dissipative Layer 7 – Conductive layer
1
6 7
Ground sense wire (to monitor)
2 3 4 5
Electrically Grounded wire fitted with 1M-ohm resistor
Figure 5, Fitting Ground and Bench Monitor Wires
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Unit Operation When steps A through I have been completed, the unit is powered and the work surface grounds are being monitored. Install operator wrist straps and ground cords. Dual snaps on the operator ground cords attach to the wristband snaps, and the mono jack plug on the other end inserts into the operator remote. (See Figure 2) The unit will power up and monitor an operators station as soon as the mono plug of the operators ground cord is plugged into the remote jack for that station. SINGLE WRIST CORD WITH BANANA PLUG
DUAL WRIST CORD WITH RIGHT ANGLE MONO PLUG
SINGLE WRIST BAND FOR GUEST
DUAL WRIST BAND MONITORED FOR OPERATOR
Figure 6 NOTE: The operator remote has two jacks. One is a 3.5mm mono jack for use with the dual wrist strap. A dual operator ground cord plugged into this jack will be monitored. The other jack is a grounded banana jack for use with a single conductor operator ground cord. This is a grounded guest hook-up. Station Grounding Fault Indication As soon as an operators ground cord is plugged into the mono jack, the work-surface and wrist strap for that station will be monitored. As long as the ground paths through the grounded worksurfaces and wrist straps are within the correct range, the green safe light on the unit will light as shown in Figure 3. The unit will continuously monitor the station and will alarm immediately upon detection of a fault condition. When a fault condition is detected the green safe light will go out, an audible alarm will sound and a fault indicator LED will light. If a fault occurs on the operator #1 station, a continuous alarm will sound. If the fault occurs on the operator #2 station, a pulsing alarm will sound.
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NOTE: The green safe light will go out if a grounding fault exits at either operator station. However, only the station that has a red or yellow indicator light on has a fault. The other station tests good and the operator may continue to work if there are no fault indicator lights for their station. The fault indicator lights assist in rapidly determining where a fault exists. The diagram opposite shows the various fault conditions that may occur. It is important to realize that when a grounding fault alarm occurs, the fault may only affect one half of the resistive loop. An operator or work surface ground path will still be intact because of the built-in redundancy of the system. Measuring the resistance from each side of the wrist strap to ground or from the work surface snap to ground depending on where the fault is indicated can perform verification of a resistive path to ground.
Figure 7
Parking A Station When an operator has to leave the work area, the wrist strap monitoring function should be powered down by unplugging their wrist strap ground cord from the operator remote. If the wrist strap and ground cord are laid across the work surface, it will be a reminder to hook back up before resuming work. When one operator powers down their station, it does not affect the monitoring of the other station, and work may continue at the other station. Powering down each station, instead of parking, eliminates false alarming each time an operator leaves the workstation. Certification Depending upon the requirements of a facility, periodic verification of the monitoring unit may be performed. To check the units operation, use Semtronics’ 62668(EN445LC) (for 10Meg Ohm range) or the 62668(EN445LC-35) (for 35Meg Ohm) Limit Comparator. Please refer to the Limit Comparator instructions for testing procedures.
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Theory of Operation Understanding the operation of the 50521 will help in troubleshooting ground fault conditions. A block diagram of the 50521 system is shown below in Figure 4. CIRCUIT BLOCK DIAGRAM OF AN EN872
RX
LED & PIEZO ALARM
TO EXTERNAL ALARM MONITOR
IM
COMMUNICATION & ALARM CIRCUIT
IM
RX: OPERATOR RESISTANCE
WRIST STRAP TEST CIRCUIT
MAT TEST CIRCUIT WORK SURFACE MAT
UNIT GROUNDING WIRE
MAT GROUNDING WIRE
Figure 4 The essential elements of this example diagram are the ground paths through the wrist strap and mat test circuits. In order for the wrist strap circuit to measure the resistance through the wrist strap to ground, it must have another ground path to complete a loop or current path. Similarly, the mat (or hard, buried conductive-layer work surface) test circuit must be connected to another ground path in addition to the work surface ground. The alternate path to ground for the work surface test circuit is through the black ground wire from the monitor unit. For this reason, if the black ground wire from the rear of the monitor unit is disconnected the work surface alarm will be indicated. Likewise, the other alarm modes of Figure 3 can be understood from a basic analysis of the block diagram. It is also easy to understand the grounding redundancy the system provides from this diagram. If an open is encountered, in one leg of a ground loop, the operator or work surface remains grounded through an alternate path. The work surface test circuit provides a redundant ground path to the wrist strap ground circuit. For additional information on Semtronics’ products, please contact you nearest distributor or our technical department in the USA at (909) 627-8178.
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TECHNICAL SUPPORT:
USA Desco EMIT 3651 Walnut Ave. Chino, CA 91710 Tel: (909) 627-8178 Fax: (909) 627-7449 NOTE: Unauthorized servicing or modifications to your monitor will void the product warranty and may create dangerous conditions. Servicing should be performed only at the factory, or by a Desco EMIT approved technician.
LIMITED WARRANTY
Desco EMIT expressly warrants that for a period of one (1) year from the date of purchase, Desco EMIT 50521 will be free of defects in material (parts) and workmanship (labor). Within the warranty period, a unit will be tested, repaired, or replaced at our option, free of charge. Call Customer Service at 909-627-8178 (Chino, CA) or 781-821-8370 (Canton, MA) for Return Material Authorization (RMA) and proper shipping instructions and address. Include a copy of your original packing slip, invoice, or other proof of date of purchase. Any unit under warranty should be shipped prepaid to the Desco EMIT factory. Warranty replacements will take approximately two weeks. If your unit is out of warranty, Desco EMIT will quote repair charges necessary to bring your unit up to factory standards. Call Customer Service at 909-627-8178 for proper shipping instructions and address. Ship your unit freight prepaid. WARRANTY EXCLUSIONS THE FOREGOING EXPRESS WARRANTY IS MADE IN LIEU OF ALL OTHER PRODUCT WARRANTIES, EXPRESSED AND IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE WHICH ARE SPECIFICALLY DISCLAIMED. The express warranty will not apply to defects or damage due to accidents, neglect, misuse, alterations, operator error, or failure to properly maintain, clean or repair products. LIMIT OF LIABILITY In no event will Desco EMIT or any seller be responsible or liable for any injury, loss or damage, direct or consequential, arising out of the use of or the inability to use the product. Before using, users shall determine the suitability of the product for their intended use, and users assume all risk and liability whatsoever in connection therewith.
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