User's Guide 1/16 th DIN ph Controller Model 48PH2 Introduction Thank you for selecting the Extech Model 48PH2 controller. This 1/16 th DIN-size controller offers dual display, high resolution measurements, two limit relays, and automatic temperature compensation. Careful use of this controller will provide years of reliable service.
Specifications ph measurement range Temperature Compensation Limit Relays (2) Hysteresis (deadband) Display resolution Measurement accuracy Display Relay status indicators Memory Back-up 0.01 to 14.00pH Automatic compensation (0-100 o C) via RTD temperature sensor or Manual compensation SPDT contacts rated for 5A (resistive) Adjustable from 0.00-2.00 ph ph: 0.01pH; Temperature: 0.1 o ph: ± (0.02pH); Temperature: ±0.5 o C 3-1/2 Digit (2000 count) Dual LED (ph: red; Temperature: green) Front panel LED indication All programming and calibration data is saved while the meter is off Automatic calibration Automatic recognition of ph 7.00, 4.00, 10.00, 1.68 and 12.45 Operating conditions Power supply Panel Cutout Meter Dimensions Meter Weight 32 to 140 o F (0 to 60 o C); 0 to 95% Relative Humidity 90 to 260VAC 50/60Hz 1/16th DIN 1.81 x 1.81" (46 x 46mm) 4.7 x 1.77 x 1.77" (105 x 45 x 45mm) 5 oz. (142g) 2
Front Panel Description 1. Unit of measure for top ph measurement display 2. Unit of measure for temperature display on lower digits 3. High Output Relay status LED indicator light is on when high relay is energized 4. CAL programming button 5. Upper display for ph measurement and programming displays 6. Lower display for temperature measurements and programming displays 7. Low Output Relay status LED indicator light is on when low relay is energized 8. SET programming button 9. UP arrow programming button 10. DOWN arrow programming button 3
Installation Mounting the Controller 1. Prepare a 1.81 x 1.81" (46 x 46 mm) panel cutout (1/8" to 3/8" thickness). 2. Slide the controller into the cutout until the bezel is flush with the panel. 3. Slide the mounting bracket over the rear of the controller and press snugly against the rear of the panel. R T D Rear View 80 260VAC 50/60 Hz ph Input Rear Panel Connections 1. Connect AC power to the terminals indicated in NO NC C NO NC C the diagram at right. LOW LIMIT HIGH LIMIT 2. Connect an RTD sensor to the terminals indicated in the diagram at right. Note that the supplied 110Ω resistor can be connected in place of an RTD to simulate 25 o C solution temperature. 3. Connect the ph electrode to the controller s BNC ph electrode input. If the ph electrode is not connected to the controller, the ph display will be all dashes. 4. Connect external devices to the HIGH and LOW Relay terminals. The SPDT (single pole double throw) relays are dry contact type and the terminal designations are: C = Common N.O. = Normally Open (contacts close when a controller setpoint is exceeded) N.C. = Normally Closed (contacts open when a controller setpoint is exceeded) Important Wiring Notes Controller wiring must be performed by qualified technicians knowledgeable of national, state, and local electrical codes and protection requirements. Improper wiring will result in meter damage and poses a risk to other equipment. For best service life, only light duty resistive circuits (1A or less) should be connected to the controller s relays. For higher current devices use a secondary relay between the controller relay and the external device. Coils are inductive loads and can cause arcing of the relay contacts. Employ a suitable snubber network (resistor/capacitor circuit) across the controller s relay terminals to prevent inductive spikes from damaging the relay contacts. The snubber component values must match the external coil for proper operation. 4
Output Relays The 48PH2 limit relays are typically used to control pumps to add acids and bases to a process in order to maintain a desired ph level. Limit relays can also be used as general alarm switches to activate a light or buzzer, for example, when a limit has been reached. Refer to the wiring instructions earlier in this manual for connection information. The output relays are switches. The Normally Open (N.O.) relay is an open switch whose contacts close when its associated setpoint value is exceeded. The Normally Closed relay is a closed switch whose contacts open when its associated setpoint value is exceeded. HIGH and LOW Relay Setpoints Relays switch state when their user-programmable setpoint is exceeded. They switch again when the limit is no longer exceeded. If the measurement exceeds the high setpoint, the high relay will switch state. If the measurement is lower than the low setpoint, the low relay will switch state. The programming steps are detailed later in this section. HIGH and LOW Deadband (Hysteresis) The Deadband feature is used to minimize relay chatter (rapid on/off relay switching) near setpoint. This is accomplished by creating a region where no relay action can occur (see diagram below). The High Deadband parameter (db.1) creates a band at the high setpoint and the Low Deadband parameter (db.2) creates a band at the low setpoint. RELAY ACTION DIAGRAM Notes on Relay Action Diagram In the area between the High Setpoint and the Low Setpoint, the labels on the relay contacts reflect the true status of the relays (Normally Open contacts are open and Normally Closed contacts are closed). No relay action can occur in the adjustable deadband regions. When the ph goes above the High Setpoint the High Relay contacts change state (Normally Open contacts close and Normally Closed contacts open). When the ph falls back below the High Setpoint, the contacts switch back (N.O. are open and N.C. are closed). When the ph goes below the Low Setpoint the Low Relay contacts change state (Normally Open contacts close and Normally Closed contacts open). When the ph goes back above the Low Setpoint, the contacts switch back (N.O. are open and N.C. are closed). 5
Programming the Setpoints and the Deadband 1. Press and hold the SET button until the display shows I_HI (High Setpoint). The display will then automatically cycle through 3 more displays: db.1 (High Deadband), 2_LO (Low Setpoint), and db.2 (Low Deadband). 2. Press the SET button when the desired parameter is on the display. For example, to adjust the Low Setpoint, press the SET button when the display is showing I_LO. 3. When the desired parameter has been selected, the top display will show the value to be adjusted. The bottom display will now show the parameter (I_LO, I_HI, etc.). 4. Use the UP and DOWN arrow buttons to adjust the SETPOINT or the DEADBAND. Selection ranges are shown in the table below. 5. Press the SET button when finished to store the new settings. 6. The table below shows the adjustment range for each of the parameters: High Setpoint (I_HI) High Deadband (db.1) Low Setpoint (2_LO) Low Deadband (db.2) Range 0.0 to 14.00pH 0.00 to 2.00pH 0.0 to 14.00pH 0.00 to 2.00pH Auto and Manual Temperature Compensation Automatic Temperature Compensation The 48PH2 measures solution temperature via a platinum 100Ω RTD sensor. As long as the RTD sensor is connected to the controller and placed in the solution under test, the controller will automatically compensate for changes in ph due to temperature changes. IMPORTANT NOTE: Before using the controller for the first time and each time the RTD sensor is replaced, the following procedure must be performed. 1. Press and hold the CAL button until the CAL display icon appears on the lower display. Within 2 seconds, press the CAL button again. 2. The display icon Pt will appear on the lower display. The upper display will flash. 3. Use the UP and DOWN arrow buttons to set a temperature on the upper display. The value entered must be equal to the difference between the actual temperature and the temperature reading. For example, if the actual temperature is manually measured to be 30 o C and the reading is 25 o C, the user would enter +5.0 o C in the controller. Note that the range of temperature that can be entered is ±10 o C. 4. After the correct value is entered, press the CAL button to exit this mode and return to the normal operating mode. Manual Temperature Compensation If neither an RTD sensor nor a simulator resistor is connected to the controller, the controller s temperature reading will be 25 o C. Use the UP and DOWN arrow buttons to set the actual temperature of the solution to be measured (the range of adjustment is ±10 o C). Use an external thermometer (mercury type, for example) to determine the solution temperature. 6
ph Calibration The 48PH2 has automatic buffer recognition technology. Frequent 2-point calibration should be performed first at ph7 and then at ph4 or PH 10, where the second point is near the ph values to be measured. Follow these steps to calibrate the 48PH2: 1. Place the ph electrode in a ph 7 buffer solution and wait for a stable ph reading. 2. Press and hold the CAL button for 2 seconds. The lower display will indicate CAL and the upper display will begin to flash the buffer ph value. 3. Wait for the controller to automatically exit the CAL mode. The display will stop flashing and the temperature value will appear on the lower display when the CAL mode has been successfully exited. 4. Rinse the electrode and then immerse it in a ph 1.68, 4.0, 10.0, or 12.45 buffer solution and wait for a stable reading (select the buffer solution that best matches the measurement that will be taken after the calibration). 5. Repeat steps 2, 3, and 4 for the second calibration buffer. 6. Calibration is complete and the controller is now in the normal measurement mode. Special note for the calibration of non-standard buffers: If the buffer solution used is not ph 1.68, 4.00, 7.00, 10.00, or 12.45, the controller can be manually adjusted to accommodate the non-standard solution. Follow these steps: 1. Press and hold the CAL button until the lower display indicates CAL. Release the button before the display begins to flash. 2. When the digits begin flashing, use the DOWN and UP arrows to adjust the upper display to match the non-standard solution value. 3. After adjusting the display to match the solution, allow the controller to automatically switch back to the normal operating mode. In the normal operating mode the lower display digits read temperature. 7
Warranty EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and workmanship for one year from date of shipment (a six month limited warranty applies on sensors and cables). If it should become necessary to return the instrument for service during or beyond the warranty period, contact the Customer Service Department at (781) 890-7440 ext. 210 for authorization or visit our website at www.extech.com (click on Contact Extech and go to Service Department to request an RA number). A Return Authorization (RA) number must be issued before any product is returned to Extech. The sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring, operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and will not be liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited to repair or replacement of the product. The warranty set forth above is inclusive and no other warranty, whether written or oral, is expressed or implied. Calibration and Repair Services Extech offers complete repair and calibration services for all of the products we sell. For periodic calibration, NIST certification on most products or repair of any Extech product, call customer service for details on services available. Extech recommends that calibration be performed on an annual basis to ensure calibration integrity. Support Hotline (781) 890-7440 Tech support: Ext. 200; Email: support@extech.com Repair/Returns: Ext. 210; Email: repair@extech.com Website: www.extech.com Copyright 2004 Extech Instruments Corporation. All rights reserved including the right of reproduction in whole or in part in any form. 8