Like most, I use the standard convention for HMI development. Green is good or go, Red is bad or stop. This standard works well for motors, solenoids, conveyors, valves, etc...But it generates confusion IMHO for high/low level detection. In my designs, low level is always fail safe low, with a '1' indicating level and a '0' indicating no level. For high level, the opposite (for failsafe operation), '1' indicating no level, and a '0' for level (which of course catches loss of power to the sensor).
The confusion comes in as to how to display them pictorially. Green/Red for level/no level works fine for low level. Green is good (material present), red is bad (no material, I need some). However, for high level when Green is good (no material) and Red (high level condition) it seems to confuse the operator because we have two graphics very close together on the same tank with green/red meaning two different things because of the nature of the sensor and its purpose.
In the case of a 'good' condition of a tank, with material between the two sensors, they would both display green. Makes sense to me, but not so much for the casual observer or untrained operator. They think the green means both sensors are covered. It's caused so much confusion that in some instances I've eliminated the point sensors graphics alltogether and developed a psuedo continous level indicator based on the states of the two sensors. Or, as an alternative, have a high level indicator only visible in the case of a high level condition.
I was just wondering what others are doing and if you run into the same confusion.
The confusion comes in as to how to display them pictorially. Green/Red for level/no level works fine for low level. Green is good (material present), red is bad (no material, I need some). However, for high level when Green is good (no material) and Red (high level condition) it seems to confuse the operator because we have two graphics very close together on the same tank with green/red meaning two different things because of the nature of the sensor and its purpose.
In the case of a 'good' condition of a tank, with material between the two sensors, they would both display green. Makes sense to me, but not so much for the casual observer or untrained operator. They think the green means both sensors are covered. It's caused so much confusion that in some instances I've eliminated the point sensors graphics alltogether and developed a psuedo continous level indicator based on the states of the two sensors. Or, as an alternative, have a high level indicator only visible in the case of a high level condition.
I was just wondering what others are doing and if you run into the same confusion.
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