LaMotte MULTI-RANGE CONDUCTIVITY METER DA-1 1929 User Manual
Page 4
NOTES ON THE USE OF THE
CONDUCTIVITY PROBE
The sensing elements of the conductivity probe consist of two carbon
elements rigidly supported in a rugged plastic material.
These elements have a very precise parallel spacing which determines the
probe cell constant. To keep this spacing and to assure accurate results, it is
essential that the probe is properly maintained and kept clean.
1.
When conductivity measurements are made, the probe must be
immersed in at least ½" of solution. The probe may be completely
immersed within the sample without adversely affecting the results.
2.
There is a tendency for the conductivity probe to entrap air bubbles
which may result in erroneous readings. After the probe is immersed
in the test solution, tap or “jiggle” the probe until air bubbles are
removed.
3.
The conductivity probe must be kept from contacting the bottom or
sides of the container which holds the sample. Contact with surfaces
other than the solution might result in inaccurate readings since the
current flow may be altered between the probe elements.
4.
After the completion of the conductivity measurement, rinse inside
and outside of probe thoroughly with water, preferably distilled water.
Allow probe to drain completely before storing. The probe may be
stored dry indefinitely without any damage.
GENERAL OPERATING PROCEDURE
1.
Plug probe into BNC receptacle (top right corner of panel).
2.
With control knob in the “OFF” position, meter pointer must
balance at zero. To adjust the zero position, use meter-zero adjusting
screw (“X” slot screw on front of meter face). The mirror-faced scale
insures accurate readings by eliminating errors due to parallax
problems which would otherwise occur when the indicating needle
and the scale are not properly aligned by the reader’s eye.
3.
Switch the control knob to the “BAT. CK” position. Meter should
indicate greater than 80 micromhos/cm. If not, replace battery.
(See instructions for battery replacement, page 8.)
4.
Set the “TEMP” knob at 25°C, the Range Selector at “X100,” and
switch the control knob to the “CAL” position. The meter should
indicate exactly 100 micromhos/cm. If not, carefully adjust by using
the “STD” knob.
4
Con duc tiv ity
Sa lin ity
0°C
5°C
10°C
15°C
20°C
25°C
30°C
0
00
23,600
27,300
31,100
35,100
39,200
43,500
47,800
28
24,400
28,100
32,100
36,200
40,400
44,800
49,400
29
25,200
29,000
33,100
37,300
41,700
46,200
50,900
30
26,000
30,000
34,100
38,500
43,000
47,600
52,400
31
26,800
30,900
35,100
39,600
44,200
49,000
53,900
32
27,500
31,700
36,100
40,700
45,400
50,300
55,400
33
28,300
32,600
37,100
41,800
46,700
51,700
56,800
34
29,100
33,500
38,100
42,900
47,900
53,000
58,300
35
29,700
34,200
39,000
44,000
49,100
54,400
59,800
36
30,500
35,100
40,000
45,100
50,300
55,700
61,300
37
31,200
36,000
41,000
46,200
51,500
57,100
62,800
38
32,000
36,800
41,900
47,200
52,700
58,400
64,200
39
32,700
37,700
42,900
48,300
53,900
59,700
65,700
40
Data derived from the equation of P.K. Weyl, Limnology and Oceanography; 9,75 (1964).
CALIBRATION
Although each conductivity meter is precalibrated before it leaves the
manufacturer, it may become necessary to check the calibration to
determine if the instrument is responding to the specifications, especially if
the conductivity probe is different from the original one supplied with the
unit. This procedure should only be attempted by qualified personnel.
Please read the instructions thoroughly before starting.
Two accurately-prepared standard conductivity solutions are required for
the calibration procedure*. These solutions may be prepared with reagent
grade potassium chloride (KCl) in the following manner:
Solution #1:
0.05M KCl: In a 1.0 liter volumetric flask, dissolve 3.725g
anhydrous KCl in deionized/distilled water and dilute to 1.0 liter mark. At
25°C this solution has a conductivity of 6,668 micromhos/cm.
Solution #2:
0.5M KCl: In a 1.0 liter volumetric flask dissolve 37.25g
anhydrous KCl in deionized-distilled water and dilute to 1.0 liter mark. At
25°C this solution has a conductivity of 58,640 micromhos/cm.
9