Industrial process indicating/recording apparatus using stepping motor drive

In a process instrument of the type having a movable device representing by its position the level of a process condition being monitored and driven by a stepping motor operated by sequential pulses from clock pulse means, feedback means for developing a feedback signal corresponding to the position of said movable device within a full-scale range of positions of said device, and deviation means for producing a deviation signal representing the difference between such feedback signal and a measurement signal;

• apparatus comprising:
• means responsive to said deviation signal for activating said stepping motor to effect corrective action tending to return said device to the position represented by said measurement signal;
• limit means for producing a limit signal when said device has come within either of two predetermined limit ranges at the respective ends of full-scale displacement of said device;
• and
• means for de-activating said stepping motor after a predetermined number of stepping pulses have been directed thereto following development of said limit signal.

In a process instrument of the type having a movable device representing by its position the level of a process condition being monitored and driven by a motor, feedback means for developing a feedback signal corresponding to the position of said movable device, and deviation means for producing a deviation signal representing the difference between such feedback signal and a measurement signal;

• apparatus comprising:
• an alarm circuit having an input receiving said measurement signal and an output circuit producing an alarm signal when said measurement signal matches an alarm set-point signal;
• adjustment means for setting said alarm set-point signal;
• switch means operable between first and second conditions;
• said switch means in said first condition directing said measurement signal to said deviation means to control the position of said movable device in accordance with the magnitude of said measurement signal;
• said switch means in said second position directing said alarm set-point signal to said deviation means to control the position of said movable device in correspondence to said set-point signal;
• whereby said adjustment means can be set to a desired signal level by observing the position of said movable device with respect to a scale as said adjustment means is varied.

In a process instrument of the type having a movable device representing by its position the level of a process condition being monitored and driven by a stepping motor operated by sequential pulses from clock pulse means, feedback means for developing a feedback signal corresponding to the position of said movable device, and deviation means for producing a deviation signal representing the difference between such feedback signal and a measurement signal;

• apparatus comprising:
• dead-band means responsive to said deviation signal for developing a control signal when said deviation signal falls outside of a predetermined dead-band about the position represented by said measurement signal;
• said dead-band means comprising first and second comparator channels each receiving said deviation signal;
• bias-signal means for setting the magnitude of said dead-band;
• means to apply said bias signal to both of said channels;
• said first channel comprising first circuit means for producing a stop/start control signal for initiating operation of said stepping motor when said device is beyond the established dead-band;
• said second channel comprising second circuit means for developing an up/down control signal identifying the direction of movement of said stepping motor when said device is outside of said dead-band.