WRS
─1B
MICROPROCESSOR MELTING POINT APPARATUS
OPERATING INSTRUCTION
Please read through these operating instruction before using
CONTENTS
I.
APPLICATION AND FEATURE………………………1
II.
SPECIFICATIONS ………………………………….…1
III.
WORKING PRINCIPLE
…………………………… 2
IV. CONSTRUCTION ………………………………….….3
V.
OPERATION …………………………………………...5
VI. MATTERS NEED ATTENTION……………………….8
VII. MAINTENANCE AND INSPECTION………………. .9
VIII. COMPLETE SET OF THE INSTRUMENT……………10
IX. COMMON BREAKDOWN AND HANDING…………11
I.
APPLICATION AND FEATURE
In according with the definition of physical chemistry, the melting point of substance
means the temperature at which the substance changes from solid state to liquid state.
In the field of organic chemistry, the measurement of melting point is a basic means
of organic chemistry, the measurement of melting point is a basic means of
recognizing the nature of substance, and is also one of the important place in the
chemical industry and medicine researches.Also, the melting-point meter is a kind of
necessary instrument in the production of medicines, perfumes, dyestuff and other
organic crystal substances.
Microcomputer melting point meter uses the technology of photoelectric detection
and temperature display by liquid crystal. Type WRS─2A could measure three
sample at the same time. It has the functions of automatic displaying of initial and
final melting points, automatic recording of the melting curves and calculating
average value. The temperature system uses the linearly corrected platinum resistor as
the detecting element, and additionally, it uses the integrated circuits to realize the
speedy setting of eight-step linearly heating rate for being selected .Since the
initial and final melting-point readings can be stored up automatically, there is no
2A
need for this function to be monitored manually. Type WRS—2 melting point meter
uses the capillary stipulated by the pharmacopoeia as the sample tube.
II.
SPECIFICATIONS
Measuring range of the melting-point: room temperature ~300℃
Setting rate of the “starting temperature”:50℃~300℃ no more than 3 min
300℃~50℃ no more than 5 min
Setting accuracy of the “starting temperature”:±0.8℃
Minimum reading of the digital temperature display: 0.1℃
Rate of the linear heating:0.2℃/min, 0.5℃/min, 1℃/min, 1.5℃/min, 2℃/min,
3℃/min, 4℃/min, 5℃/min
Deviation of linear heating rate: no more than 10% (setting value)
Accuracy of measuring the melting-point: ＜200℃±0.5℃
200℃~300℃±0.8℃
Repeatability: 0.3℃(rate is 1℃/min), 0.2℃(rate is 0.2℃/min)
Size of the capillary: φ1.4mm(outside diameter)
φ1.0mm(inside diameter)
Loading height of the sample: 3mm
Power source: 220V±22V, 100W,50Hz
Dimensions: 398mm×278mm×210mm
Weight(net): 12.5kg
RS232 interface: band rate 9600,1 bit stop, 8bits data
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III.
WORKING PRINCIPLE
The working principle of the instrument is based on the following fact: when a
substance is in its crystal state, it reflects the light, when it is melted state, it transmits
light. Therefore, in the process of melting, a transition of the transmissivity will occur
with the rise of the temperature.
Transmissivityδ
B
A
Ta
Tb
Temperature T
Fig.1
Fig.1 shows a typical melting curve (the temperature-transmissivity curve). In Fig. 1,
the temperature ta(to which point A is corresponding) is called initial melting point;
and the temperature tb (to which point B is corresponding) is called final melting point
(or full melting point). The length of ta- tb is called melting range (or melting interval).
Type microcomputer melting point meter uses photoelectric method to detect the
change of the melting curve automatically. When the temperature reaches the initial or
final melting point, the data will be displayed and stored until next measurement.
Fig.2 shows the principle of the instrument. After going through the optical fibre, the
light, given out, by the incandescent lamp through the transmissive holes of the
electric furnace and the capillary tube-socket, and focuses on the inside of the
capillary. The light penetrating the melting sample is received by the silicon
photoelectric cell. When the temperature rises, sample is melting, the light flux
increase, then display the temperature of initial, final melting point and curve after
microcomputer processed the data. Temperature test adopts the platinum resistance as
detector inserting capillary tube-socket bottom directly, the signal pass through
linearity correction, voltage amplification, set to A/D converter, keyboard into
heating rate. D/A converter digital (setting temperature) analog voltage (Vg), adds
another analog voltage (Vto), its deviation signal through a regulator drive heating
execution. When the actual temperature signal of the furnace is higher then the analog
temperature, the cooling fan will be turned on, so that the temperature will begin to
decrease. When the actual temperature is lower than the analog one or does not reach
the desired starting temperature, the heating current increase. With the system, the
furnaces’s following function can be realized.
2
Capillary
Photoelectric Cell
Photoelectric Cell
Photoelectric
Amplifer
Heating
exection
Platinum Resistance
Light Source
Cooling Fan
High Accuracy
Constant Current
Melting
Curve
Meltin
Point
detection
+
Vt0
Σ
-
D/A
A/D
A/D
Vg
Microcomputer
Temperature
Display
Linearity
Correction
Set and heat
Fig.2
Remark: WRS—2 only one sample
IV. CONSTRUCTION
2 Insert Capillary
1 LCD
3 Reset
reset
4 Keyboard
Fig .3
Fig.3 shows the front view of the instrument.
3
operating presentation
Start_T 75
Now_T 75
℃/min
Up_Rate 1.0
℃
δ
final melting point temperature
initial melting point temperature
T
Smelt 79.8
Fmelt 80.6
n＝3
n＝3
Fig.4
Smelt: average of initial M.P. Fmelt: average of final M.P.
Operation presentation:
1) “E123”—not insert capillary press “heating” key or starting temperature too high
2) ↑— heating
3) ↓— cooling
4) press “ CAL” (calibration) key:
i “OK C”—if the measurement is valid (three final M.P. of WRS—2A are intensive or
curve of WRS—2 is continuous), press “OK”; if the measurement is invalid(final
M.P. is disperse or curve is not continuous),press “C”.
ii “A”—calibrating
5) “123C”—press “CLR”(clear)key,123 mean number of the curve
Fig.4 shows the LCD of the instrument
7
8
9
4
5
6
1
2
3
0
HEAT
reset
CLR
CAL
Fig.5
Fig.5 shows the operation of keyboard
4
Power switch
Fuse
3.15A
Fuse
1A
RS232 Interface
Electric outlet
Fuse socket（1）
4 Fuse socket（2）
Fuse(BGXP-1A-20)
Fuse(BGXP-3.15A-20)
Fig.6
Fig.6 shows the back view of the instrument
RS232 Interface
1 connect RS232 RX point
2 connect RS232 TX point
3 the earth shielded teminal
Fig.7
Fig.7 shows the RS232 interface
V. OPERATION
A. Routine measuring of the melting point
i.
Turn on the power switch (see l in Fig.6), screen display the starting
temperature and rate of the last time. After stabilized for 20 minutes,
the cursor stop at “Start_T”( starting temperature see left first line in
Fig.4),keyboard into or modify the “Start_T”, then press “  ”key.
After enter the temperature, the cursor moves to “Up_Rate”(heating
rate see right first line in Fig.4).
ii.
Keyboard into rate, then press “  ”key. After that, the cursor returns
to “Start_T”.
iii.
Using “  ”key can move cursor to the position you want to modify.
iv.
When the actual temperature of furnace arrived setting temperature,
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stabilized, insert the sample capillary (WRS—2A one, two or three
capillary, WRS—2 only one capillary).
v.
Press “HEAT”(heating) key, operating presentation “↑”(see right
second line in Fig.4), the apparatus begin to measure the sample. (If
you forget to insert the sample capillary, press “heating” key, screen
will display En, “n” shows the number of furnace, not display “↑”.)
vi.
When arriving the temperature of initial or final melting point, screen
will display the value and curve. (The meaning of data please see
Fig.4)
vii.
If not cut off power source, the data will be stored.
Remark: Loading quality of the sample will affect the accuracy of measuring
reading. The curve appearing wave hollow or discontinuous long distance is
result from bad loading.
viii.
If the user want to measure other sample, input “Start_T”, press “  ”
key, this moment the instrument will clear the curve automatically
and begin to measure the new one.
ix.
Use “CLR” key: after finishing measurement every time, the
apparatus display three curves. For some factors, you don’t satisfy the
result. You could clear the curves and measure again. Operation as
following:
① Press “CLR”key, operating presentation “1 2 3 C”.
② Input the number of curve you want to clear. Press “CLR” key again,
finish the operation of “clear”
Remark: from left to right, the number is 1, 2, 3; clear one curve, the
average value will change.
③ After inputting the working parameters, insert the sample
capillary ( need not insert the capillary into furnace you don’t
measure this time), then press “HEAT” key.
④ WRS—2A display “En”, “n” shows the number of furnace you
not measure.
x.
Use “CAL” key: long time use or season changing could result in
larger error of measurement. The user should calibrate the instrument
in order to ensure the precision. Operation as following:
① Press “CAL” key, display as Fig.8.
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Start_T 75
Now_T 75
Up_Rate 1.0
Adjust
δ
℃
0-------Default
1-------Reset
T
Smelt
Fmelt
Fig.8
② Press “0” key, recover the factory default value, press “1” key,
set again. Display as Fig.9.
Start_T 75
Now_T 75
Up_Rate 1.0
Adjust
δ
℃
Temp1
Temp2
Temp3
T
Smelt
Fmelt
Fig.9
a) The user could set the final melting point of standard sample
according to own demand (one point, two points or three
points calibration all could), press “  ”key, the apparatus
will measure as above method. (If the temperature is less
than 100 ℃ , you should input “0” at hundred digit, for
example “80.6”, input “080.6”.)
b) When finishing measure one sample, operating presentation
“OK C”. Three final M.P. of WRS — 2A are intensive or
curve of WRS—2 is continuous, press “  ” key; if the final
M.P. is disperse or curve is not continuous, press “clear” key
and measure again.
c) Operating presentation “A”, enter calibrating state. “A”
disappear, finish calibrating.
③ Press “CLR” key again, exit calibration state.
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Remark: when calibration, setting temperature should 5℃ lower
than standard sample’s final M.P; the rate of heating is 1℃/min. The
accessory standard samples have sealed up. Take off the seal when
using.
xi.
Use “RESET” key: press this key on top right corner when the
instrument is off work or refresh the operating state.
B. Connect with computer
i.
Use RS232 cable connect melting point meter and computer.
ii.
Insert the disk with the meter into computer.
iii.
When computer enter win9X, executing WRS—2A program(detail in
file Readme).
VI.
MATTERS NEED ATTENTION
i.
ii.
iii.
iv.
v.
The sample must be baked in accordance with the requirements, and
pulverized in a dry and clean crushing bowl. Use the“free-falling”
method to knock the capillary, so as to make a firm loading of the
sample. On the other hand, loading height of the sample must be
identical.
After being turned on, the temperature of the furnace will be rise to the
starting temperature of last time. If the temperature is higher or lower
than the desirable temperature, keyboard can be used to set speedily.
Don’t set up the starting temperature exceeding the application range of
the instrument. If not, the instrument will be destroyed.
Different starting temperature of some samples will affect the result of
measurement. So certain operational standards should be fixed.If the
linear heating rate of “1℃/min” is selected, the starting temperature
should be lower than the melting point by 3-5℃; and if the linear
heating rate of “3℃/min” is chosen, the starting temperature should be
lower than the melting point by 9-15 ℃ . Usually, the optimum
measuring condition should be decided in accordance with the
experiments.
Since different linear heating rates will lead to inconsistency results of
the measurements. It is necessary to set up certain standards. The higher
the rate is, the greater the reading value will be. Thus, the melting point
reading value of each step of rate can be unified by use of the
experimental correction value. Before precisely measuring those samples
(the melting point values of which are not known), the speedy heating
or high rate may be used first to obtain the approximate melting point
value.
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vi.
vii.
viii.
ix.
x.
VII.
If there is a standard sample, it can be measured first. According to
the requirements, with the same starting temperature and heating rate
to perform comparison measurement. The initial and final melting
point readings of standard sample can be used as the basis for check.
If you have a melting point standard powder, the standard powder can
be used as the temperature transmission standard; and the results can
be corrected in accordance with the nearby readings of the standard
powder.
The sample to be measured had better to be loaded in five capillaries
at a time. After being measured respectively, the mean value of the
three intermediate readings is considered as the result of the
measurement, so that the accidental error induced by the preparation
of sample and loading of capillaries can be eliminated.
After measuring the higher melting point sample, measure the lower,
you could input its “starting temperature” directly and press “cooling”
key.
For a few colored sample with poor melting characteristics or the
completed carbonized samples, the plastic cut -slice and micro
samples can be measured by type WRX-1S thermal values analyzer
with microscope. The high molecular products such as polymer can
be measured by type WQD-1A dropping point and softening point
apparatus.
Before inserting the capillary into the instrument, the stains and dirt
on the outface should be wiped off with a piece of soft cloth,
otherwise, the dirt will be accumulated on the bottom of the socked
after several times, and this will lead to the failure of the test.
MAINTENANCE AND INSPECTION
i.
ii.
iii.
The instrument should be used in a dry and ventilated room. The
instrument should be prevented from touching any water by all means,
and it should be kept from being moistened. It uses a three cores power
supply plug. The ground terminal should be connected to the earth,
which can not be replaced by neutral line.
The capillaries used in the instrument must be the products provided by
our factory. Never use the capillaries drawn manually. They are easy to
break. The capillaries used in precision measurement should be picked
and chosen.
When the capillary is broken in the tube socket, the power source
must be turned off first. After the furnace is cooled down, insert a
piece of 1mm drill (an accessory) into the broken capillary. Then lift
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the drill slowly, so as to take out the capillary. If there are some
broken glasses in the tube socket, you can pull tube socket out, glasses
can be poured out or knocked out. If also not clear completely,
you can use the drill to break glasses, then pour out them. Put the tube
socket to the former position in accordance with the original direction
(the notch of the furnace). Finally, the instrument should be checked.
If having some problem, please connect with our repair department.
iv.
when measuring, display “En”, maybe the following reason:
i)
Starting temperature too high
ii)
Forget inserting the capillary with sample
iii)
Bad loading
v.
Accuracy test: the accuracy testing should be carry out with three samples
to be tested with heating rate 1.0℃/min, such as naphthalene (final M.P.
81.00℃), adipic acid (final M.P. 152.89℃), anthraquinone (final M.P.
285.96℃) Are applied. The measurement should be carried out for five
times respectively, with starting temperature’s being set less 5℃ than
final M.P.. The testing result can be found from the mean value of the
remainder three intermediate reading which has been deleted the
minimum and maximum. The deviation would be coorrespondent
stipulated accuracy.
vi.
Repeatability test: under the specified heating rate 0.2℃/min and 1.0
℃/min, the same conditions of the sample preparation, the
measurement of the melting point standard powder (sulfanilamide) is
performed for five times. If the standard deviation (℃)is calculated
in accordance with the following formula, the deviation will be less
than the specified tolerance:
 x i  x 
n
S＝
2
i 1
n 1
Where: x i ─ the measured value (℃) of each time;
x ─ the mean value (℃);
n ─ times of the measurement(=5)
vii.
Calibration: see step “V/x”
Beg to inform user:
i)
Check final M.P. value of standard periodically, if no obvious change
occur, need not indicating value calibration
ii)
Dry samples strictly, fill it in capillary firmly, otherwise, the
calibration value will be beyond the scope of standard.
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VIII. COMPLETE SET (REEER TO PACKING LIST)
IX.
COMMON BREAKDOWN AND HANDING
Breakdown Appearance ANALYSES FOR REASON
Turn on the instrument, No power source.
no display.
The fuse is broken.
Others.
Value not accurate.
Parts are broken.
The change of environment
Is large
Computer no display
The lines connected with
RS232 are not correct.
The program is wrong
Handing method
Connect with power source.
Change fuse.
Send to our repair department.
Calibrate again.
Check the lines and weld well
Send to our repair department.
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