Choosing a magnetic safety sensor for movable machine guards means balancing price, package size, and condition. The four options here span $100 to $250, from a used Keyence single unit to a lot of three Pilz sets, so your decision will likely hinge on how many positions you need to monitor and whether you want a matched actuator included.
Quick take
The Keyence GS-M51P is the lowest listed price at $100. The Pilz lot is the highest at $250 but gives you three complete sets with actuators. The SCHMERSAL BNS33-11ZG-2128 is an open-box set with a matching actuator, while the BNS 33-12ZG is a new single sensor that sits between the two price points.
Listed-price comparison
| Product | Listed price | Price bar |
|---|---|---|
| SCHMERSAL BNS33-11ZG-2128 with Magnet Actuator 101148482 | $215 | |
| 1PC BNS 33-12ZG Schmersal Magnetic Safety Sensor | $153 | |
| Pilz (x3) PSEN ma1.4 Magnetic Safety Switch Sensor Sets 506301 w/ -50 & (2) -52 | $250 | |
| Keyence GS-M51P Safety Interlock Switch Non-Contact Safety Sensor | $100 |
Decision matrix
| If you need... | Consider... | Listed price |
|---|---|---|
| The lowest listed price for a single non-contact safety sensor | Keyence GS-M51P | $100 |
| A new single Schmersal sensor below $200 | BNS 33-12ZG | $153 |
| An open-box Schmersal set with a matching actuator | BNS33-11ZG-2128 with Magnet Actuator | $215 |
| Multiple sensor sets in one purchase | Pilz PSEN ma1.4 lot | $250 |
Product notes
SCHMERSAL SAFETY MAGNETIC SENSOR BNS33-11ZG-2128 with Magnet Actuator 101148482
This open-box Schmersal set is the only option that bundles a safety magnetic sensor with its matching magnet actuator. At $215, it's the second-highest listed price, reflecting the included actuator and German origin. The DC current type and coded-magnet reed switch design make it suitable for movable guards and robot arms. If you need one complete, matched set rather than multiple pieces, this is the straightforward route. The limitation: you receive one set only, and the open-box condition means it isn't a sealed new product. If you need to cover more than one door, you'll be buying additional sets.
1PC BNS 33-12ZG Schmersal Magnetic Safety Sensor ID179748 Machine Safety Control
At $153, this new Schmersal sensor is the mid-point option. It's a single sensor, new condition, with a stated Country of Origin of China. It doesn't include the actuator that the Schmersal BNS33-11ZG-2128 set includes, so it's a better fit if you already have an actuator or are replacing a damaged sensor head. The $62 difference relative to the Schmersal set is significant if you're watching cost, but you'll need a compatible actuator if you don't already have one. For a replacement or expansion, this single unit is a budget-conscious way to stay with Schmersal hardware.
Pilz (x3) PSEN ma1.4 Magnetic Safety Switch Sensor Sets 506301 w/ -50 & (2) -52
This $250 lot is the highest listed price, but it covers three positions. It includes three PSEN ma1.4 sensors and three actuators: one -50 variant and two -52 variants. That means you can protect three separate guard doors or machines in one purchase. The M8 quick-connect fittings and attached cables are part of the package, and all pieces are new open-box. The mixed actuator variants offer slightly different mounting/orientation options for different installation setups. The trade-off is the per-piece cost: if you only need one set, this lot is more than the single Schmersal set, and you'll have two extra sets to store or use later.
Keyence GS-M51P Safety Interlock Switch Non-Contact Safety Sensor Made in Japan
This is the lowest listed price at $100, making it the entry option. It's a used Keyence unit from a working automation system, sold as the exact unit photographed. It's rated for DC current and has a digital output, and it was professionally removed from working equipment. The Japanese origin is stated in the title. The main limitation is that it's used, not new, and it is a single sensor without a matching actuator. If your budget is tight and you're comfortable with used industrial components, this is the most affordable way to get a KEYENCE safety interlock switch into your setup. If you require all-new components with a matched actuator, one of the Schmersal or Pilz options will be a better fit.
Final recommendation by use case
- Lowest listed price: Keyence GS-M51P at $100, for a used single sensor.
- New single Schmersal sensor: BNS 33-12ZG at $153, for systems that already have an actuator.
- Complete matched Schmersal set: BNS33-11ZG-2128 at $215, with actuator included.
- Multi-position coverage: Pilz PSEN ma1.4 lot at $250, for three sensor sets.
