Black & Decker DCM200C Guía de instalación descargar pdf (Pagina 25)

DCM 200 Installation

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5.7. Frequency Controlled Pumps, Contacts 4 & 5

Sets the variable frequency control range for pumps controlled by sensors A..C.

Not applicable to pumps controlled by volume meters or contact set F.

Method Function Examples

Always

Frequency varies proportional to

sensor value when value between

Turn ON and Turn OFF setpoints.

Proportional acid or oxidant

controls.

Substitutes for more

expensive 4-20mA controlled

pumps. Can also select PID

control functions in addition

to strictly proportional

control.

During Events

Control active during events until

event volume pumped.

Periodic flocculent feed

during a timed feed event.

5.3.3. Special Control Responses

Multiple Types of Control For Standard Relays

Time Modulation: Relays 1-5

Application: Cycles a chemical feed pump ON/OFF, decreasing the ON time as the

controlling sensor approaches the Turn OFF setpoint.

Typically used for pH control, reducing acid feed rate as the Turn OFF setpoint is approached.

Use if you can’t use a variable pulse frequency controlled pump.

Setup: User selects a relay & selects Time Modulation in Special Control.

User sets Period in seconds, minimum 60 (recommended), Default is currently at 120 Seconds,

maximum is 600 seconds.

Operation: Relay ON 100% of Time Period when Control is beyond Turn ON setpoint.

Relay ON time = [ (Control – Turn OFF Setpoint) / Deadband ] x Period

where Deadband = Turn ON – Turn OFF setpoints.

Relay is OFF when Control is beyond Turn OFF setpoint.

Example: Acid Pumps Turn ON = 7.52 pH and Turn OFF = 7.50 pH. Period = 60 seconds

At pH >= 7.520, Pump ON for 60 seconds in every 60 seconds [100% of Period]

At pH = 7.515, Pump ON for 45 seconds in every 60 seconds [75%]

At pH = 7.510, Pump ON for 30 seconds in every 60 seconds [50%]

At pH = 7.505, Pump ON for 15 seconds in every 60 seconds [25%]

At pH <= 7.500, Pump OFF [0%]

Notes: Time Modulation control is not advisable when the system response time is faster

than 5x the Period. In the previous Example; If the measured pH moves from 7.52 to

7.50 in less than 300 seconds, Time Modulation may not hold pH more stable.

Process buffering, pump setting, feed point and system volume all affect the

response to chemical feed.

Time modulation works on both Rising or Falling Setpoints.

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