Quick take
When a machine guard needs an interlock, the real choice is matching a magnetic safety sensor to the number of guard points, the wiring setup, and the condition tolerance your maintenance team can accept. The four options here cover a bare sensor, a multi-set package, a matched sensor-and-actuator pair, and a stop-motion detector. Use the quick take to shortlist, then check the price comparison and product notes.
If you need just the sensor element, the BNS 33-12ZG is the new-condition pick. If you need to cover multiple guard doors, the Pilz PSEN ma1.4 lot is the multi-set package. If you want one complete sealed pair, the Schmersal BNS33-11ZG-2128 with magnet actuator is the direct route. If your machine already runs on a stop-motion detector, the stop-motion option is the one to weigh.
Listed-price comparison
| Product | Listed price | Price bar | Condition | What you get |
|---|---|---|---|---|
| 1PC BNS 33-12ZG Schmersal Magnetic Safety Sensor | $153.00 | New | Single magnetic safety sensor unit | |
| Pilz (x3) PSEN ma1.4 Magnetic Safety Switch Sensor Sets 506301 w/ -50 & (2) -52 | $250.00 | New - Open box | Three sensors, two actuator variants | |
| SCHMERSAL SAFETY MAGNETIC SENSOR BNS33-11ZG-2128 with Magnet Actuator 101148482 | $215.00 | New - Open box | Sensor, magnet actuator | |
| Prewired Stop Motion Detector Safety Machine 3 Way Interlock Release See Info | $185.52 | Used | Prewired detector, three-way interlock release |
Decision matrix
Need a bare sensor without an actuator? Start with the BNS 33-12ZG. Need sensors and actuators for multiple guard doors in one purchase? The Pilz PSEN ma1.4 lot is the only multi-set option here. Need a complete single-set pair? The Schmersal BNS33-11ZG-2128 with magnet actuator is the one that explicitly pairs sensor and actuator. Need a detector with an interlock release? The stop-motion detector is the alternative to inspect.
Product notes
1PC BNS 33-12ZG Schmersal Magnetic Safety Sensor
This is the entry point in the group and the most direct: one BNS 33-12ZG magnetic safety sensor, listed as new. If you need to replace the sensor element on an existing guard and the actuator side is already handled, the single-unit format avoids buying components you don't need. The limitation is baked into the product name: the 1PC designation means a single sensor unit, so a multi-door installation will require additional purchases. The new condition is the main offset against the sparser packaging.
Pilz PSEN ma1.4 Magnetic Safety Switch Sensor Sets (3 Sets)
The Pilz package is the completeness play. It includes three PSEN ma1.4 sensors, one -50 actuator, and two -52 actuators, all with attached cables and M8 quick-connect fittings. That makes it the most direct way to outfit three safety gate positions from one package. The actuator variants are the trade-off: the -50 and -52 differ in mounting and orientation, so track which actuator goes where during installation. The condition is new open box, meaning the protection is there but the packaging may show signs of handling.
SCHMERSAL SAFETY MAGNETIC SENSOR BNS33-11ZG-2128 with Magnet Actuator
This Schmersal set provides the sensor and its matching magnet actuator in one package, so you don't need to source a separate actuator. It offers a 1NO/1NC reed-switch arrangement, a 4-pin M8 connector, and an IP67 thermoplastic enclosure, making it well suited to movable guards and articulated robot arms where a sealed connection matters. The limitation is that the actuator is bundled in, so you can't buy just the sensor side if that's all you need. It is new open box and lists a chassis mounting type.
Prewired Stop Motion Detector Safety Machine 3 Way Interlock Release
This is the only used option in the group and it takes a different approach: a stop-motion detector with a three-way interlock release, listed as prewired. The unit carries the part number Allen Bradley CU2 and a country of manufacture of the United States. The prewired design can save a wiring step if you're replacing a similar detector on an existing line. The used condition is the main limitation, since a pulled component carries less certainty than a new unit. If your application calls for this style of interlock release, it deserves a side-by-side look with the new options.
Final recommendation by use case
- Sensor-only replacement: Choose the BNS 33-12ZG at $153.00 if you need a new sensor element and the actuator side is already covered.
- Multi-door installation: Choose the Pilz PSEN ma1.4 lot at $250.00 if you need sensors and actuators for multiple guard positions in one purchase.
- Matched pair for a movable guard: Choose the Schmersal BNS33-11ZG-2128 with magnet actuator at $215.00 if you want a complete sensor-and-actuator set with a sealed enclosure.
- Stop-motion detector replacement: Choose the Allen Bradley CU2 detector at $185.52 if the condition trade-off fits your maintenance strategy and you need a stop-motion unit.
