Question
What is negative operation and positive operation?
Answer
(A) Negative operation | (B) Positive operation | (C) Combined operation | ||||
Safety | Never use negative-operation switches alone in safety applications. | Positive-operation switches are recommended when used alone as the switches offer a higher level of safety than negative-operation switches. | Switches in combined operation offer an even higher level of safety than positive-operation switches alone. | |||
Category | Category B or 1 (using approved parts) | B, 1, 2, 3, 4 | B, 1, 2, 3, 4 | |||
Operating status | Normal operation | Abnormal operation | Normal operation | Abnormal operation | Normal operation | |
Contacts closed (door closed) | a) No reset due to contact welding (door open) | Contacts closed (door closed) | a) Contact not open due to cam abrasion (door open) | Contacts closed (door closed) | ||
Contacts open (door open) | b) No reset due to spring damage (door open) | Contacts open (door open) | b) Contact not open due to improper cam position (door open) | Contacts open (door open) | ||
Contact opening method | Opened by built-in spring. | Opened directly by externally operating unit like cam or dog. | Opened by a negative- and positiveoperation combination. | |||
Applicable contact | NO contacts | NC contacts | NO and NC contacts | |||
Char- acter- istics | Pros | The negative operation is a fail-safe operation that ensures safety in case of cam abrasion, improper cam positioning or unexpected cam removal. | The actuator forcibly opens contacts if a contact welds or a spring is broken. | A negative- and positive-operation combination eliminates the disadvantages of both modes. | ||
Cons | The actuator may move accidentally with unexpected force and close the contacts. The result may be a relatively dangerous situation. | There is a danger that contacts may close due to cam abrasion, improper cam positioning or unexpected cam removal. | The safety switch circuit may work normally for a while if one of the switches fails to operate. |
For Safety Light Curtain Robust & Basic New Lineup. Understanding the Indicators at a Glance.
Compact (104.5 mm), lightweight (1.3 kg) and easy-to-install Safety Laser Scanner
Supports ISO 13849-1 (PLe/Safety Category 4). Can be used on higher risk level applications by connecting to Safety Controllers.