Topworx GO™ Switch Introduction
GO™ Switches operate on the principle of magnetic attraction, reacting to ferrous metal or magnetic targets as they come within the switch's sensing range.Although switches vary in design according to their intended applications, all GO Switches use permanent magnets which, when actuated by the presence of a ferrous or magnetic target, change the state of electrical contacts.
70 Series GO™ Switch Mounting
- 70 Series GO Switches are unaffected by weld fields and RF interference.
- 70 Series GO Switches may be mounted adjacent to or surrounded by ferrous metals however the proximity of ferrous metals will affect sensing distance. For the maximum rated sensing distance, avoid mounting near ferrous metals.
- GO Switches sense ferrous materials such as mild steel, 400 series and 17/4 stainless steel.
- Sensing and differential of switch may vary depending on target travel direction.
- Avoid contact between target and switch. Configure mounting of switch and/or target so that target passes within the sensing area. Sensing range will vary according to model number and mass of target used.
- Target magnets, available through TopWorx, will increase the sensing range of the switch. Reference sensing ranges in corresponding sections throughout the catalog.
- For optimum performance, provide sufficient mass of target, and choose the appropriate GO Switch model to match the application requirements for operating frequency, type of load, etc.
- Greater target mass and target movement fully into and out of sensing range will increase contact pressure. This is helpful in low current controls applications.
- For heavy or inductive loads, arc suppression devices, or interposing relays are recommended for contact longevity. Contact factory for specifics.
- Do not use excessive force on external threads when installing. For typical installations: Torque 3/8" threads to 60lbs-in (7 Nm) max. Torque 5/8" threads to 35 lbs.-ft. (47 N-m) max. Consult TopWorx technician for special installations.
- Configure mounting so bracket dissects switch as close to the middle of the body as possible. This eliminates undue stress caused by heavy cables, connectors, etc.
- Two appropriately sized jam nuts are included with switch. Lock washers are recommended where vibration is present.
70 Series GO™ Switch Specifications - SPDT
Sensing Distance:71 & 72: .040" (1.02mm) 2,000 PSI
73-77, 7L: .100” (2.54mm) 2,000 PSI
73-77: .072” (1.83mm) 5,000 PSI
73-77: .060” (1.52mm)10,000 PSI
Range with Target Magnet: Up to .35” (Model 71 & 72 up to .15")
Differential:
Approx. .020" (.5mm)
Thread Options:
71, 72: 3/8-24 UNF; M12 x 1
73-76, 7L: 5/8-18 UNF; M18 x 1
Response time: 8 milliseconds
Temperature Rating:
71-77: -40ºF (-40ºC) to 221ºF (105ºC) Std.*
71-77,7G, 7H: HiTemp to 400ºF (204ºC)*
7L: -40ºF (-40ºC) to 160ºF (71ºC)*
* Reference certificates for variations to temperature rating.
Contact Material: Palladium silver with Sawtooth® surface configuration
Contacts:
Single Pole, Double Throw, Form C
Electrical Ratings: Resistive
71-77:
4A @ 120VAC/3A @ 24VDC
2A @ 240 VAC/1.25A @ 48VDC
7L: .25A @ 120VAC/24VDC (approx. 5V drop)
Target Material: Ferrous metal; optional target magnets
Conduit Outlet: 1/2" -14NPT. One location
Enclosure Material: Stainless steel type 303, 316 optional; 7L - 316 stainless steel
Repeatability: .002" (0.05mm) Under identical operating conditions
70 Series GO™ Switch Specifications - DPDT
Sensing Distance: .090" (2.3mm) end sensing (2000 PSI)Range with Target Magnet: up to .20” (5mm)
Differential: Approx. .020"(.5 mm)
Thread Option:
7G, 7H: 5/8"-18 UNF; M18 x 1
7I: 1"-14 UNF
Response time: 8 milliseconds
Temperature Rating:
-40°F (-40°C) to 221°F (105°C)*
HiTemp option to 400°F (204°C)*
* Reference certificates for variations to temperature rating.
Contact Material: Palladium silver with Sawtooth™ surface configuration
Contacts:
Double Pole Double Throw, 2 Form C.
Electrical Ratings: Resistive
3A @ 120VAC/1A @ 24VDC
Target Material: Ferrous metal; Optional target magnets
Enclosure Materials: Stainless Steel type 303, 316 optional
Conduit Outlet: 1/2”-14 NPT. One location
Repeatability: .002" (0.05mm) typical under identical operating conditions
Setting Up A 70 Series GO Switch For Optimum Performance
GO Switch 70 Series end sensing switches use three permanent magnets and a push pull plunger to control a set of mechanical contacts. The center magnet simultaneously attracts the primary magnet and repels the bias magnet, pushing the connecting rod and common contact into the normally closed position, closing a contact circuit. When a ferrous or magnetic target enters the sensing area of the switch, it attracts the primary magnet, which pulls the connecting rod and common contact. The normally closed and normally open contacts change state.The sensing distance is the maximum distance between the switch and target when the switch first operates; the trip point. The differential, also known as deadband or hysteresis, is the distance that the target must move from the sensing area in order to allow the switch to reset.
To apply the 70 Series GO Switch and obtain the least differential, the direction the target approaches the switch must be considered. Below are two possible orientations that illustrate the differences in target movement and the affects on switch differential.
The measurements shown are nominal and can vary as much as .030-.050” depending on the material and size of target used in the application. As you can see, the best scenario for least differential is to orient the switch and target as shown in Orientation B. However, in this application, the possibility of getting debris between the switch and target must also be considered.
When trying to determine differential of an application, it is directly proportional to the distance the target will travel in the application. For example: a linear valve stroke is 1”. A switch is applied to indicate the closed position of the valve.
Using Orientation A, the differential is 0.090 “. The ‘deadband’ is therefore 9% of travel. If the switch were re-oriented, as shown in the Orientation B, the deadband would be only 2% of the total valve travel. Remember, there is no exact science to use when applying a GO Switch. However, once the switch is set, and the target travels to the same position every time (within .002”), the GO Switch will maintain calibration for life. Set it and forget it!
Attachment of Conduit or Cable to 70 Series GO™ Switch
Attach conduit or cable correctly.- When using long runs of conduit or cable, place supports close to the switch to avoid pulling switch out of position.
- If switch is mounted on a moving part, be sure flexible conduit is long enough to allow for movement, and positioned to eliminate binding or pulling.
- For installation in hazardous locations, check local electrical codes.
- All conduit connected electrical devices, including GO Switches, must be sealed against water ingression through the conduit system. In figure 1, something common has occurred, the conduit system has filled with water. Over a period of time this may cause the switch to fail prematurely. In figure 2, the termination of the switch has been carefully filled with electronics grade RTV to prevent water ingression and to prevent premature switch failure. A drip loop with provision for water to escape has also been installed. For hazardous locations install per Electrical Code. Dry contact devices, such as GO Switch, maybe installed intrinsically safe with matched barrier. When installed as explosion proof, lead seal fittings required within 18" of switch.
All GO Switches are "pure" contact switches, meaning they have no voltage drop when closed, nor do they have any leakage current when open. For multi-unit installation, switches may be wired in series or parallel, as shown below.
GO™ Switch 70 Series Wiring
Any number of GO Switches may be wired in series, without voltage drop. By contrast, solid state switches have about two volts drop across the switch when operated. In a 12 volt solid state system with four switches in series, 8 volts is dropped across the switches. Only 4V is left to operate the load. When using GO Switches, 12V is still available to operate the load. (Except 7L - approx. 5V drop)GO™ Switch 70 Series Parallel Wiring
When solid state switches are placed in parallel, there is about 100 microamps leakage through each switch. If ten solid state switches were wired in parallel, the total leakage current would be 1000 microamps or one milliamp - sufficient current to indicate an "ON" condition to a programmable logic controller (PLC). Any number of GO™ Switches may be wired in parallel, with no current leakage and without drawing operating current. (Except 7L - approx. 5V drop)
Air and Hydraulic Cylinders
A ferrous cylinder cushion or piston will actuate the switch. To determine the correct thread length, measure the distance from the head cap surface to the cushion and add 1/2" for seal nut.Thread seal nut onto switch. Screw switch into cylinder by hand until switch touches cushion. Back out 1/4 to 1/2 turn. Tighten seal nut.
Cylinder Applications Switch Sealing Torque Values
Models 71-72:
3/8" Diam/12mm
Torque Jam Nuts to:
15 lbs-in to achieve seal at 2,000 PSI
30 lbs-in to achieve seal at 5,000 PSI
Do not exceed 60lbs.-in (7N-m)
Models 73-76 & 7L:
5/8" Diam/18mm
Torque Jam Nuts to:
15 lbs-ft to achieve seal at 2,000 PSI
25 lbs-ft to achieve seal at 5,000 PSI
Do not exceed 35lbs.-ft (47 N-m)
Special Conditions for Safe Use and Possible Misuse
- The oversheathed or individual conductors must be suitably protected against mechanical damage and terminated within a terminal or junction facility suitable for the conditions of use.
- Three wire/three pin devices are not provided with an external connection facility for the earthing or bonding conductor. It is the user's responsibility to ensure adequate earth continuity via the mounting arrangements.
- Both contacts of the Double Throw and the separate poles of the Double Pole switch, within one proximity switch must form part of the same intrinsically safe circuit.
- The proximity switches do not require a connection to earth for safety purposes, but an earth connection is provided which is directly connected to the metallic enclosure. Normally an intrinsically safe circuit may be earthed at one point only. If the earth connection is used, the implications of this must be fully considered in any installation. i.e. by the use of a galvanically isolated interface.
- The switch must be supplied from a Certified Ex ia IIC intrinsically safe source.
- The flying leads must be terminated in a manner suitable for the zone of installation.
- An external ground connection must be protected by an external mounting device and / or cable connections / conduits.
- For 74 Series switch, temperature and environmental temperature are marked T6 / T85 ° C (-20 ° C ≤ Ta ≤ +50 ° C).
Ex d IIC, Ex tD A21 IP66 T85°C (Tamb = -20°C to +50°C)
Ex d IIC, Ex tD A21 IP66 T200°C (Tamb = -40°C to +150°C)
For 74 Series with Niltox cable only. Ex d IIC T6 Gb, Ex tb IIIC T85C Db, IP66 (Tamb –20°C to +50°C)
Baseefa08ATEX0360X
IECEx BAS 08.0122X
120VAC/4A AND 24VDC/3A FOR SPDT SWITCHES
120VAC/3A AND 24VDC/1A FOR DPDT SWITCHES
Ex d IIC T6 Gb, Ex tb IIIC T85°C Db IP66 (-40°C < Ta < +50°C)
Ex d IIC T4/T3 Gb, Ex tb IIIC T135°C/T200°C Db IP66 (-40°C < Ta < +100°C/150°C)
For 74 Series Niltox cable only:
Ex d IIC T6 Gb, Ex tb IIIC T85°C Db IP66 (-20°C < Ta < +50°C)NCC 12.1268X
Ex ia IIC T6 Ga, Ex ia IIIC T85°C Da (Tamb = -40°C to +50°C)
Ex ia IIC T4 Ga, Ex ia IIIC T135°C Da (Tamb = -40°C to +100°C)
Ex ia IIC T3 Ga, Ex ia IIIC T200°C Da (Tamb = -40°C to +150°C)
Baseefa09ATEX0173X
IECEx BAS 09.0080X
Ui = 30V and Ii = 250mA
Reference Baseefa Certificate for special conditions. All area classifications are dictated by the model number. Reference GO Switch brochure for complete listing.
For 7L Series GO Switch with “E” approval the following statements apply:
- This equipment is suitable for use in Class I, Division 2, Groups A,B,C & D, Class II, Division 2, Groups F&G and Class III or non-hazardous locations only.
- Warning-Explosion Hazard- Substitution of components may impair suitability for Class 1, Division 2.
- Warning-Explosion Hazard - Do not disconnect equipment unless power has been switched off or the area is known to be non-hazardous.
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Email: mechanicalsales@forberg.com
