Bips and Bops

First week on the job. You are riding with your mentor, trying to absorb everything, trying not to look lost. He is talking about a controller he needs to check out and he says, casually, "Pull up the bips and bops on that thing." You look at him. He looks at you. He is not smiling. He is not joking. BIP: Binary Input Point. BOP: Binary Output Point. Welcome to building automation, where the terminology was apparently designed by people who never had to explain it to anyone.

Let us start with binary because it is the simpler concept. Binary means two states. On or off. Open or closed. Energized or de-energized. There is no middle ground. A flow switch is either proving airflow or it is not. An occupancy contact is either closed or open. A high limit switch is either tripped or it is not. When the controller reads a binary input it gets one bit of information: yes or no. That is it. That is a binary signal.

Analog is the opposite. An analog signal exists on a range; it is not yes or no, it is "how much." A temperature sensor does not say hot or cold. It says 72.4°F. A pressure sensor does not say high or low. It says 1.43 inches of water column. A humidity sensor says 47.2% relative humidity. The controller reads a voltage, a resistance, or a current value from the sensor and converts it into a number with engineering units. That number can be anything within the sensor's range. That is an analog signal.

Here is where it gets fun. Every manufacturer in this industry decided to name these things differently. Trane calls them BIPs and BOPs: Binary Input Points and Binary Output Points. Johnson Controls says BI and BO. Distech says DI and DO: digital in, digital out. Some platforms say AI for analog input, some say AIP, some just say "Analog Input" with no abbreviation at all. And then there are universal inputs, UI, which can be configured as either analog or binary depending on what you connect. It is a mess. It was always a mess. It will probably always be a mess.

The good news: once you understand what a binary input actually does, it does not matter what anyone calls it. The concept is the concept. A flow switch closing a circuit is a binary input whether the software labels it BI1, BIP-1, DI_01, or "FlowProof." You will learn the naming conventions for whatever platform you end up on. The understanding travels with you everywhere.