Transcript ALPHA-pH1000 controller

lpha-2000 Series
Process Controllers
lpha pH/ORP 2000
lpha CON 2000
lpha DO 2000
Eutech Instruments
FEATURES of lpha2000 Series
• ASIC-based with intelligence and
flexibility - matrix format programming
• User-selectable functions that can be
customized to suit one’s requirements
• On-line push-button calibration
• Built-in non-volatile memory backup
FEATURES of lpha2000 Series
• Multi-level password protection - avoid
unauthorized tampering of the system
• Auto/Manual selection for control function
• HOLD function
• Proportional and Proportional Integral
Control - Pulse length/Frequency
PROPORTIONAL VS PROPORTIONAL INTEGRAL
AMPLIFIER
SETTING
+
PROCESS
OUTPUT
ERROR SIGNAL
FEED BACK
SUMMING
+
ERROR SIGNAL
INTEGRATOR
-
PROCESS
OUTPUT
AMPLIFIER
+
+
PI CONTROL - ERROR CORRECTION
Correction in %
120
100
80
PI Control
60
40
P Control
20
0
0
2
4
6
8
10
Integration Interval
12
14
16
FEATURES of lpha2000 Series
• 14 segment LCD display
• Backlit ‘Transflective’ LCD
• Two current outputs
• Choice of 0/20 or 4/20 mA
• 22mA for ‘Out of Range’ condition
• Push-button display of set points
FEATURES of lpha2000 Series
• Zoomable transmitter output
• Galvanically isolated signal output
• Isolated 12V/50mA DC output
• On/Off delay time for Set point relays
• Set point Relay state programmable
FEATURES of lpha2000 Series
• Hi/Lo feature for set-points
• 4 Relays, 2 for Setpoints, Alarm and Wash
• On-delay for Alarm relay
• Hysteresis band -- prevent signal overshoot from
false triggering & on/off continuously
HYSTERESIS
RELAY ON
RELAY OFF
4
4.5
SP1
FORWARD DIRECTION
7
9.5
10
SP2
SP1 Set to LO
SP2 set to HI
HYSTERESIS BAND ( DEFAULT 0.5 pH )
REVERSE DIRECTION
The controller relay activates when the set point is reached. In the reverse direction, it
does not de-activate when the value reaches the set point. Instead, it continues to be
active till the value reaches the amount set by the Hysteresis band.
FEATURES of lpha2000 Series
• Choice of Pt100 or Pt1000
• Temperature in Centigrade or Fahrenheit
• Two wire or three wire system
• Choice of ATC or MTC -- independent Temp
setting for Process and Calibration
• Switched Mode power supply
FEATURES of lpha2000 Series
• 80 to 250 V AC/DC auto detect
• Detachable back panel connectors
• Standard 144x144mm front panel
• Protection against EMI with CE mark endorsed
• IP 65/NEMA 4X rated field mount housing
–
W series
FEATURES of lpha-pH2000 Series
• pH/ORP mode of operation, both in one
controller
• ORP mV or ORP % mode of operation
• Symmetrical or Asymmetrical input
• Choice of use with Glass or Antimony electrode
FEATURES of lpha-pH2000 Series
• Auto buffer recognition - choice of 7 buffers
• One point Cal choice of 7.00 or 6.86 pH
• Electrode status display after calibration
• On line offset adjustment for pH and Temp
CHARACTERISTIC CURVE OF CONTROLLER
LIMIT CONTROLLER
100%
50%
PROPORTIONAL
CONTROLLER
SP1 Xp = 0
SP2 Xp=0
100%
50%
Prop. Band Xp
Prop. Band Xp
FEATURES of lpha-CON2000
• 2 cell or 4 cell operation
• Wide range up to 1000 mS/cm
• User selectable – 7 ranges
• Cell constant input for automatic
correction
• Cell constant from 0.005 to 9.999
FEATURES of lpha-DO2000
• mg/l , ppm or % saturation mode of operation
• Extended range 0 to 300%, 0 to 25 mg/l
• Pressure compensation for the % sat. mode
• Auto calibration in the % saturation mode
• Choice of two cells: 0-10 or 0.5 - 40 ppm
• Pressure input in mmHg and Kpa
Differential pH
Measurements
Combined Electrode Pair
Conventional Technique
E1
E2
100 MEG
E1- E2
pH
Glass
Electrode
E1
E2
pH
Reference
Electrode
Conventional Construction
E1
E2
100 MEG
E1- E2
E2
E1
pH
Reference
Electrode
pH
Glass
Electrode
Pitfalls of Conventional pH
• Plugging junction
• Poisoning of the
internal element
• Rapid electrolyte
depletion
• Ground loops
Technique Comparison
• Combination
Electrode
• Differential Electrodes
Preamplifier
Benefits of Differential pH
• Reduced cost of ownership
• Long life with glass reference electrode
– Replaceable quad junction salt bridge
– Buffered electrolyte (typically 7pH)
• Long sensor to analyzer distances without
coax
• Low impedance reduces noise pickup
• Ground rod eliminates ground loops
• Adjustable isopotential point
Reference Solutions
Standard Combination pH Reference
Reference Electrode
Solution
• Reference solution when
using silver/silver
chloride wire
• 4 Molar KCL with AgCL
Differential pH Reference
7 pH Buffer
• Reference solution
when using pH glass
• 0.05 Molar Potassium
Phosphate, pH
adjusted with NaOH
Differential Technique
Preamplifier
E1 - E3
-(E2 - E3)
(E1 - E2)
Temperature
Compensator
Process Reference Solution
Electrode Electrode Ground
(E1)
Electrode
(E2)
(E3)
Differential pH at its Best
• Differential pH measurement
• Two protected pH glass electrodes
• Ground rod
– Accurate temperature measurement
– Up to 1000 foot cable
• Very large reference chamber
– Replaceable solution
– Volume resists contamination
– Any reference from 2 pH to 10 pH
• Long-lasting salt bridge
– Quad junction
– Replaceable
– Smooth surfaces reduce fouling.
1.5 Inch NPT threads
Huge internal
reference chamber
Replaceable
quad junction
salt bridge
Low profile
pH glass
Six wrench flats
Short 6-inch body
Smooth surfaces
reduce chance of
fouling
Ground rod
•
•
•
•
Easy Replacement
O-Ring sealed
Quad Junction
Seals in sanitary
fittings
Cutaway
Reference Electrode
Amplifier
Ground
Rod
Reference Buffer
Active Electrode
O-ring seals
Quad Junction
Bridge
pH Sensor Care
• Dehydration
• Detrimental factors to electrode life
– Abrasion
– Coating
– Temperature Shock
• Transportation
• Storage
pH Sensor Cleaning
Hot water and detergent
For normal applications.
5% to 10% HCL acid
For solutions containing lime
and hydroxides.
Bleaching liquid
For solutions with algae,
bacteria and molds.
Competition
• GLI (Patent 3,709,796 and 3,862,895)
• Rosemount
•E+H
• ATI
• Aquametrics
Instumentation
?
Alpha pH 2000D