JENCO 6250 User manual

OPERATION MANUAL
MODEL 6250/6219 SERIES
MICRO COMPUTER BASED
PH/mV/ION/TEMP METER
JENCO ELECTRONICS, LTD.
MANUFACTURER OF PRECISION INSTRUMENTS

1
General Description
The bench type model 6219 and portable type model 6250
pH/mV/Ion/TEMP meter are precise instrument for the measurement of pH,
mV, ion and temperature.
A built in micro computer stores, calculates and compensates for all the
relevant parameters relating to pH determinations, such as the temperature
characteristics of the pH electrode, buffer solutions and electrode slope
deviations, etc.
This two models can measure specific ion concentration directly in the
ION mode. The ION mode provides a digital readout in any concentration
units.
The RESOL. key can select different resolution of pH and mV
measurements.
Additional features such as splash proof touch keys with audio feedback,
buffer recognition, electrode slope recognition, ATC (Automatic
Temperature Compensation) capabilities, temperature measurement to 0.1
degree C, visual and audio operational error indications, simplicity of
operations, large LCD display can display pH (mV/ion) and
temperature values of the sample simultaneously., etc., make the 6219 and
6250 ideal "USER FRIENDLY" instruments for field (model 6250) or
laboratory (model 6219) applications.
The instrument is powered by six AA-size (model 6219) / AAA-size
(model 6250) alkaline batteries or AC adaptor. When the batteries are in
need of replacement, the LCD will display a "LO BAT" message.
Initial Inspection
Carefully unpack the instrument and accessories. Inspect for damage in
shipment. If any damage is found, notify your JENCO representative
immediately. All packing materials should be saved until satisfactory

2
operation is confirmed.
The model 6250 and model 6219 are used 4.01pH, 7.00pH and 10.01pH
standard buffer. The model 6250C and model 6219C are used 4.00pH,
6.86pH and 9.18pH standard buffer. Make sure the model number is that
you ordered.
POWER SOURCE
The Jenco model 6250 operate on either six AAA size alkaline batteries or
AC adaptor. The model 6219 operate on either six AA size alkaline
batteries or AC adaptor. Insert batteries as described below.
BATTERY INSTALLATION
1. Replace batteries when the LOBAT annicator on the LCD display
starts to flash. The meter can operate within specifications for
approximately one hour after LOBAT starts to flash. But you
must replace the new batteries when OFF is display, ie. automatic
turn OFF to prevent incorrect measurements.
2. AOpen battery compartment by pushing closure up. This is most
easily open by using a coin (such as a penny) and inserting it into
the slot on the side of the meter. (model 6250)
2. B Open battery compartment by pushing closure up and lift the
battery cover to expose the battery compartment.(model 6219)
3. Insert the batteries and ensure polarity is correct as shown in
Figure 1.
4. Replace battery compartment cover.
TURN OFF INSTRUMENT
When the instrument is not in use, press the ON/OFF or POWER key to
turn off the instrument. Un-pluging the AC adaptor from the instrument or
from the AC line does not turn off the instrument. It would automatically
switch to the internal batteries. The instrument will continue to operate on
the internal batteries.

3
Figure 1 Battery Compartment

4

5

6

7
Figure 4
SPECIFICATIONS
Model 6250 6219
Range -2.000 to 16.000 pH
pH Accuracy +/-0.1% +/- 1 digit
Resolution 0.01 pH or 0.001 pH (selectable)
Range -1999.9 to 1999.9 mV
mV Accuracy +/-0.1% +/- 1digit
Resolution 1 mV or 0.1 mV (selectable)
Range -5.0 to 125.0
TEMP Accuracy +/-0.5
Resolution 0.1
Range 0.00 to 119.8 conc.
ION Accuracy +/-2LSD
Resolution 0.05 conc. (range 0.00 to 25.00 conc.)
0.1 conc. (range 25.00 to 50.0 conc.)
0.2 conc. (range 50.0 to 119.8 conc.)
Operating temperature 0 to 50
Power supply Six AAA batteries Six AA batteries
9V AC adaptor 9V AC adaptor
Display pH/mV/ion 15mm high LCD 12.7mm high LCD
TEMP. 8.7mm high LCD 12.7mm high LCD
Batterylife 25Hours 50HOurs
Dimensions (W/D/H) 83mm/241mm/72mm
250mm/240mm/100mm
WEight (w/batteries) 450gm 1070gm
Touch Keys for Model 6219 and Model 6250

8
1. ON/OFF (POWER) key: The ON/OFF (POWER) key toggles the power
of the instrument on and off. The current mode and pH/ion calibration
values are saved to the internal non-volatile memory of the instrument
when turned off and restored when turned back on.
2. MODE key: The MODE key selects the display mode of the instrument.
Pressing the MODE key cycles the display sequentially from pH, mV and
ion. THe calibration values are not affected by changing the display modes.
3. STAND/STAND I, SLOPE/STAND II key: The STAND/STAND I and
SLOPE/STAND II keys are for standardizing the instrument only.
4. UP and DOWN key: These keys are used to manually enter the
temperature values. The UP key increments the temperature, while the
DOWN key decrements the temperature. These keys will not respond
when operating in the automatic temperature compensation (ATC) mode.
5. RESOL. key: The RESOL. key toggles the resolution of the instrument
in pH or mV mode. But not for ion mode.
6. CLEAR key: The CLEAR key is used to reset the instruments mode and
clear the pH/ion calibration values. The CLEAR key has a delayed
reaction of 2 seconds before responding to protect from accidential key
presses. However, When the instrument display an error the CLEAR key is
pressed, all the LCD segments and annuciators will be on for a 2~3
seconds and the instrument will enter into the pH mode. The CLEAR key
is intended to be used only when errors are made that require the
instrument to be recalibrated.
MEASUREMENT ERROR INDICATIONS
Er1 1. pH electrode offset greater than +/- 1.5 pH range
2. Buffer 7.00pH (model 6250/6219), 6.86pH (model 6250C/6219C)
not correct
Er2 1. pH electrode slope off by more than +/- 30 % of ideal slope
2. Buffer 4.00pH, 9.18pH (model 6250C/6219C), 10.01pH (model
6250/6219) not correct
Er3 Temperature out of the -5.0 to 125.0 degree C range
Er4 Buffer temperature out of the 0 to 50.0 degree C range
Er5 1. pH values out of the -2.000 to 16.000 pH range when in pH mode
2. mV values out of the -1999.9 to 1999.9 mV range when in mV

9
mode
3. Ion values out of the 0 to 119.8 conc. range when in ion mode
OPERATIONAL PROCEDURES
pH CALIBRATION
Connect the AC adaptor to the AC power line. Make sure the correct AC
adaptor is used. It is recommended to conserve the internal batteries by
using AC power whenever it is available. Turn on the instrument by
pressing the ON/OFF (model 6250)/ POWER (model 6219) key. The
instrument will enter into the state when the instrument was last turned off.
It is not necessary to press the CLEAR key. You also can press RESOL.
key to select the optimum resolution you need.
1. Calibration with ATC/Temp probe in the pH mode.
A triaxle 3-in-1 pH/Ref/Temp electrode with user's electrode cable, can be
used in place of a combination pH electrode and a separate ATC/Temp
probe.
1.1 Connect the pH electrode and the ATC/Temp to the connectors of the
instrument. Refer to the Figure 2. The ATC annicator (model 6250)/ green
color ATC LED lamp (model 6219) will be on. Press the MODE key to
enter into pH mode, the pH anniciator (model 6250) or pH LED
lamp (model6219) will on and the STAND anniciator (model 6250) or
green color STAND LED (model 6219) will flash.
1.2 Rinse the pH electrode and ATC/Temp probe in distilled water and
immerse in pH 7.00 (model 6250/6219) or pH 6.86 (model 6250C/6219C).
The instrument will display the buffer temperature.
1.3 Allow sufficient time for the electrode and ATC/Temp probe to
stabilize. Press the STAND/STAND I key. The STAND indication will
be on and the SLOPE annicator (model 6250) or SLOPE green
color LED lamp (model 6219) will flash, indicating that standardization at
buffer 7.00pH or 6.86pH is complete and the instrument is ready to be
sloped at a second buffer. The instrument will display the buffer value

10
corresponding to the temperature of the buffer 7.00pH or 6.86pH as
measured in 1.2.
Refer to Table 1. If the reading still drifts, repeat 1.3 until a stable reading
is obtained.
If Er1 is displayed, check to make sure that the correct buffer is used and
that the electrode offset is less than +/- 1.5pH. Replace the buffer and/or
the pH electrode. Press the CLEAR key and repeat from 1.2. Er1 may
appear if the STAND/STAND I key is pressed before the electrode and
ATC/Temp probe settle to within +/- 1.5pH of the buffer value. Allow
sufficient time for the electrode and ATC/Temp probe to stabilize before
taking any action.
If Er4 is display, The buffer temperature is out of the 0 to 50.0 degree C
range. Bring the buffer temperature within range and repeat 1.2. It is not
necessary to press the CLEAR key.
1.4 Remove the pH electrode and ATC/Temp probe from buffer 7.00pH or
buffer 6.86pH, rinse with distilled water and immerse in buffer
4.01pH, 10.01pH (model 6250/model 6219) or buffer 4.00pH, 9.18pH
(model 6250C/ model 6219C). The instrument will display the
temperature of the second buffer.
1.5 Allow sufficient time for the pH electrode and ATC/Temp probe to
stabilize. Press the SLOPE/STAND II key. The SLOPE indication
will stop flashing and stay on. The instrument will display the
second buffer value corresponding to the temperature of the second buffer
as measured in 1.4. Refer to Table 1. If reading still drifts, repeat 1.5 until a
stable reading is obtained. The micro computer inside the instrument will
calculate and compensate for the pH electrode slope deviation
corresponding to the values of the two calibration buffers. The instrument
is dual point calibrated and is ready for measurements.
If Er2 is display, check to make sure that the correct buffer is used and that
the slope of the electrode is not off by more than +/- 30% from the
theoretical slope. Replace the buffer and/or the pH electrode. Press

11
CLEAR key and repeat from 2.2. Only buffer 4.01 and 10.01 (model 6250/
model 6219 only) or Buffer 4.00 and 9.18 (model 6250C/ model 6219C
only) may be used to slope the instrument. Er2 may appear if the SLOPE
key is
pressed before the electrode and ATC/Temp probe settle to within +/- 30%
of the buffer value. Allow sufficient time for the electrode and
ATC/Temp probe to stabilize before taking any action.
If ER4 is displayed, the buffer temperature is out of the 0 to 50.0 degree C
range. Bring the buffer temperature within range and repeat 1.2. It is not
necessary to press the CLEAR key.
2. Calibration with manual temperature compensation in the pH mode
2.1 Connect the pH electrode to the instrument. Refer to Figure 2.
The MANUAL indication MAN (model 6250) or red color
MANUAL LED lamp will be on. (Per Figure 3) Press the
MODE key for the instrument enter into pH mode , the pH
indicator wil on and the STAND anniciator (model 6250) or green
color STAND LED lamp(Model 6219) will start flash (Per Figure 3).
2.2 Rinse the pH electrode in distilled water and immerse in buffer
7.00 (model 6250/ model 6219) or 6.86. (model 6250C/ model 6219C)
Set the instrument to display the temperature of the buffer 7.00
or 6.86 by pressing the UP or DOWN key.
2.3 Pressing the UP key will increase the temperature and the DOWN
key will decrease the temperature. The displayed temperature must be
within 0.0 to 50.0 defree C range.
2.4 Allow sufficient time for the electrode to stabilize. Press
STAND/STAND I key. The STAND indication will be on and the
SLOPE anniciator (model 6250) or green color SLOPE LED lamp
(model 6219) will flash, indicating that standardizaion at buffer
7.00 or 6.86 is complete and the instrument is ready to be sloped at a
second buffer. The instrument will display the buffer value
corresponding to the temperature of the buffer 7.00 or 6.86 set in 2.2,
2.3. Refer to Table 1. If the reading still drifts, repeat 2.4 until a
stable reading is obtained.
If Er1 is display, check to make sure that the correct buffer is used and

12
that the electrode offset is less +/- 1.5 pH. Replace the buffer and/or the
electrode. Press CLEAR key and repeat from 2.2. Er1 may appear if
the STAND/STAND I key is pressed before the electrode settles to
within
+/- 1.5 pH of the buffer value. Allow sufficient time for the electrode
to stabilize before taking any action.
2.5 Remove the pH electrode from buffer 7.00(model 6250/ model 6219)
or 6.86(model 6250C/ 6219C), rinse with distilled water and
immerse in buffer 4.01 or 10.01 (model 6250/ model 6219) or
4.00 or 9.18 (model 6250C/ model 6219C). Set the instrument to
display the temperature of the second buffer, as in 2.3. The
displayed temperature must be within 0 to 50.0 degree C range.
2.6 Allow sufficient time for the pH electrode to stabilize. Press
the SLOPE/STAND II key. The SLOPE indication will stop flashing
and stay on. The instrument will display the second buffer value
corresponding to the temperature of the second buffer as set in 2.5.
Refer to Table 1. If the reading still drifts, repeat 2.6 until a stable
reading is obtained. The micro computer inside the instrument will
calculate and compensate for the pH electrode slope deviation
corresponding to the values of the two calibration buffer. The
instrument is dual point calibrated and is ready for measurements.
If Er2 is displayed, check to make sure that the correct buffer is used
andthat the slope of the electrode is not off by more than +/- 30%
from the theoretical slope. Replace the buffer and/or the pH electrode.
Press CLEAR key and repeat from 2.2. Only buffer 4.01 and 10.01
(model 6250/ model 6219) or buffer 4.00 and 9.18 (model 6250C/
model 6219C) may be used to slope the instrument. Er2 may appear
if the SLOPE/STAND II key is pressed before the electrode settles to
within +/- 30% of the buffer value. Allow sufficient time for the
electrode to stabilize before taking any action.
pH MEASUREMENTS
The STAND and SLOPE indications must be on, indicating that the
instrument is dual point calibrated and ready for measurements.

13
1. Measurement with ATC/Temp probe in the pH mode.
1.1 Removed the pH electrode and rinse with distilled water and
immerse it in the sample to be measured and the ATC anniciator
(model 6250) or green color LED lamp (model 6219) will
be on (Per Figure 3). The pH unit , ATC, STAND and SLOPE
indicators are on .
1.2 The display will track the pH value as sensed by the pH
electrode and the ATC/Temp probe. Allow sufficient time for
the display to stabilize. The instrument will display the pH
value of the sample at the displayed sample temperature.
If Er5 is displayed, the pH value measured is out of the
-2.000 to 16.000 pH range.
2. Measurement with manual temperature compensation in the pH
mode
2.1 Connect the pH electrode to the connector of the instrument.
Refer to Figure 2.
2.2 Press the MODE key enter into pH mode, the pH , STAND, SLOPE
indicators is on and the MANUAL anniciator (model 6250)
or red color LED lamp (model 6219) are on . (Per Figure 3)
2.3 Rinse the pH electrode with distilled water and immerse it in the
sample to be measured.
2.4 Use the UP and DOWN keys to set the sample solution's
temperature.
2.5 Allow sufficient time for the display to stabilize. The instrument will
display the pH value of the sample at the set
sample temperature.
If Er5 is displayed, the pH value measured is out of the -2.000 to
16.000 pH range.

14
TEMPERATURE MEASUREMENTS
The two model 6250/6219 can be used to measure temperature
independently with ATC/Temp probe with using the pH electrode.
1.1 If the pH electrode is not connected to the instrument, the pH input
must shorted to the reference input by the protect cap.
1.2 Connect the ATC/Temp probe to the input connector. Refer to
Figure 2. The ATC/MANUAL LED lamp will change from red
color to green color and enter into ATC mode.
1.3 Place the temperature sensor in the media to be measured. The
measured temperature is displayed.
Er3 will be displayed if the temperature is out of the temperature
measurement range -5.0 to 125.0 degree C. Once the temperature
brought within range, Er3 will disappear and the correct
temperature reading will be displayed. It is not necessary to press
the CLEAR key.
Er4 will be displayed if the temperature is out of the temperatue
range 0 to 50.0 degree C, Please press MODE key to enter into mV
or Ion mode for the other measurements.
mV MEASUREMENTS
A combination electrode can be used in place of the working electrode and
the reference electrode. The MANUAL indication will be on if the
ATC/Temp probe is not connected to the instrument.
1.1 Connect the working electrode to the input BNC connector and the
reference electrode to the input Pin connector. Refer figure 2.
1.2 Press the MODE key for the instrument to enter into mV mode
and press RESOL. key to select optimum resolution.

15
1.3 Rinse the working and reference electrode with distilled
water and immerse the two electrode in sample to be measured.
1.4 Allow sufficient time for the display to stabilize. The
instrument will display the millivolt value of the sample.
If Er5 is displayed, the millivolt value measured is out of the
+/-1999.9 mV range. The instrument will display the correct value
once the input millivolt is brought within range. It is not necessary
to CLEAR the instrument.
1.5 The ATC/Temp probe can be used to measure the sample
temperature as required.
ION MEASUREMENTS
The following rules should be observed in order to make accurate
determinations of ion concentration.
Rule A. All hardwares used to handle ion standards and samples should
always be cleaned with deioned water.
Rule B. THe standard solutions and samples should always be at the
same temperature.
Rule C. A magnetic stirrer should be used for all measurements of
standards and samples.
Rule D. Study the instruction manual of the ION sensor carefully to
make sure that the proper ionic strength adjuster and/or pH
adjuster is used.
1.1 Connect the ION sensing electrode to the BNC connector and
the reference electrode to the REF pin connector.
1.2 Prepare 2 standards 1 decade apart. The concentration of the
sample should be within the range of the 2 standards. The 2
standards can be of any concentration unit such as ppm, mg/l
or M.
1.3 Rinse the electrode with the dilute standard or de-ionized
water and immerse the electrodes in the dilute stanard 1.
1.4 Press Mode key to enter into ION mode. The LCD display

16
will display ION , anniciator 1 ( on the higher left
cornor / model 6250) or red color STAND I LED (model 6219)
lamp will flash and the conc. unit indicator will on. 1.5 Press the
STAND/STAND I key, the LCD will display 1.00, anniciator 1
(on the higher left conor / model 6250) or STAND I LED
lamp (model 6219) will on and anniciator 2 (on the higher
left cornor/ model 6250) or red color STAND II LED (model
6219) lamp will flash. The instrument is single point standardized
and assumes a slope of +58 mV per decade change in
concentration.
Er5 will be displayed if the input value exceeds +/- 750mV
(approximately) or the display exceeds 120.0 conc.
Er2 will be display if the STAND II key is pressed before the
STAND I key.
1.6 For dual point standardization, remove the electrodes from the
dilute standard, rinse with the concentrate standard or de-
ionized water and immerse the electrodes in the concentrate
standard 2.
1.7 Press the STAND II key, the anniciator 2 (model 6250)
or STAND II LED (model 6219) lamp will on. The STAND II
key can be pressed as many times as required for a stable reading
of 10.00 conc. The instrument is dual point standardized and
ready for measurements. The electrodes should always be rinsed
with the sample or de-ionized water before measure-ments.
Er2 will be displayed if electrode slope small than 50% of
ideal slope, 58 mV.
Er5 will be displayed if the input value exceeds +/- 750 mV
(approximately) or the display exceeds 120.0 conc.

17
TEMPERATURE COEFFICIENT OF pH BUFFERS
BUFFERS
TEMP(C) 4.01 6.86 7.00 9.18 10.01
0 4.003 6.982 7.119 9.460 10.321
5 3.998 6.949 7.086 9.392 10.248
10 3.996 6.921 7.058 9.331 10.181
15 3.996 6.898 7.035 9.276 10.120
20 3.999 6.878 7.015 9.183 10.064
25 4.004 6.683 7.000 9.183 10.014
30 4.011 6.851 6.988 9.143 9.968
35 4.020 6.842 6.979 9.107 9.928
40 4.030 6.836 6.973 9.074 9.891
45 4.042 6.832 6.969 9.044 9.859
50 4.055 6.831 6.968 9.017 9.831
The actual reading of the instrument can differ from the values shown by
+/- 1 digit.
TABLE 1
The value in TABLE 1 is stored in the memory of the microcomputer.
Since the buffer values stored is the value of the buffers at 0, 5, 10, 15, 20,
25, 30, 35, 40, 45 and 50 degree C. It is recommended to keep the buffers
at above temperatures or close to room temperature to minimize the error
of the buffer.

18
Operating the Meter Using the RS232C Interface
INTRODUCTION
This section assumes you are familiar with the basic of data
communication, the RS232C interface, rudimentary knowledge and a
copy of any of the following computer languages: Turbo Basic, Quick
Basic, Turbo PASCAL and Turbo C.
This meter can only be operated using the RS232C interface by using the
software driver included with this meter and writing a simple
program to send and receive data from the meter using any of the
above mentioned computer languages.
An annotated sample programs for each computer language and amore
detailed explanation of the software driver are included in the
accompanying disk.
PREPARING THE METER FOR OPERATIONS VIA THE RS-232C
INTERFACE
The Meter comes equipped with an RS232C (serial) interface. The
meter communicates with a PC computer (100% IBM PC/AT compatibles)
through a DB-9 interface connector (model 6250) or DB-25 interface
connector (model 6219). using a standard RS232 cable for interconnecting
two IBM PC/ATs can be use.
Connecting the cable and turning on the meter and the computer, you
are now ready for the software part of the operation.
SOFTWARE PREPARATION
The accompanying disk includes a special software driver to let you
easily write a simple program to read data from the meter. By

19
incorporating the driver to your software you can then use the special
commands without worrying about the protocol between the meter and
your computer.
For the model 6250 Reading "MAN6250.TXT" in the accompanying disk
will jumpstart you to using the meter with its RS232C interface.
"MANUAL.TXT" is the general explanations of the various serial
commands available in the driver.
For the model 6219 Reading "MAN6219.TXT" in the accompanying disk
will jumpstart you to using the meter with its RC232C interface.
"MANUAL.TXT" is the general explanations of the various serial
commands available in the driver.
MODEL 6250/ MODEL 6219 RS232 PARAMETERS
BAUD RATE : 2400 (FIXED)
PARITY : SOFTWARE DRIVER CONTROLLED
DATABITS : 8
STOPBIT : 1
PROTOCOL : SOFTWARE DRIVER CONTROLLED.
WARRANTY
Jenco Instruments, Ltd. Warrants this product to be free from significant
deviations in material and workmanship for a period of 1 year from date of
purchase. If repair or adjustment is necessary and has not been the result of
abuse or misuse, within the year period, please return-freight-prepaid and
the correction of the defect will be made without charge. If you purchased
the item from our Jenco distributors and it is under warranty, please contact
them to notify us of the situation. Jenco Service Department alone will
determine if the product problem is due to deviations or customer misuse.
Out-of –warranty products will be repaired on a charge basis.