If this voltage is applied to the positive input
terminal of a slave recorder through a potential
divider, which decreases this 1-Ov to the voltage
required for full-scale deflexion of the recorder, and,
if the negative terminal of the recorder is connected
through a ten-point stepping switch to a chain of
resistors giving voltage steps each equal to the fullscale-deflexion
voltage, the problem is solved. For
example, if the recorder has a range of lmv, the
potential divider must give a 1000-fold voltage
decrease and the resistor chain must give 1 mv steps.
Circuit. Fig. 1 shows the circuit of the unit as
designed for an auxiliary recorder of lmv fullscale
deflexion. The unit itself is shown to the left
of the broken line; the components shown on the
right of the line are already present as parts of the
circuitry of the Beckman DK2 instrument and
R2a
0-9 White
-0-7 kSl
I6 Linear potentiometer -.06 R8, 500kS2(0
< LI A=0
-0 4 Recorder,
R4 500
-0-2 Grey
o.
OFFl
l 45n _15(tv5f
Fig. 1. Circuit of extinction scale-expansion unit. The
unit is shown on the left of the broken line; the components
on the right of the line form part of the existing circuit of
the Beckman DK2 spectrophotometer, as set for extinction
measurements. The numbered squares represent the
terminal lugs to which wires are taken from the unit. 'A'
denotes 'absorbance' as shown by the position of the pen
of the Beckman DK2 instrument. Resistors B3 and R4
form the 1000-fold potential divider (more accurately 999-
fold, but the scarcely detectable difference is within the
tolerance of the resistors, and in any case is taken care of
by the initial adjustments).
require no modification. The circuit is shown as it
appears when in use for extinction measurements.
The logarithmic potentiometer that controls the
pen movements under these conditions is not shown.
The chain of resistors on the left is supplied from
the same stabilized voltage source within the
Beckman DK2 instrument as supplies the linear
potentiometer, so that in effect the whole arrangement
forms a bridge. The pre-set potentiometer
R2 is adjusted once for all so that each 10Q
resistor gives 1 mv. Resistors R3 and R4 form
the potential divider. No alterations to the
Beckman DK2 instrument are required, but three
wires are taken from the unit to the lugs numbered
6, 7 and 10 of the terminal block (TB 1903) within
the case of the instrument at the end nearest the
lamp-house. The unit is left permanently connected
even when not in use; the resistor chain uses a
negligible current, and the shunting effect of R3 on
the potentiometer is also negligible (and in any case
is eliminated by the usual initial adjustments), so
that there is no detectable effect on the transmission
or extinction measurements.
If this voltage is applied to the positive input
terminal of a slave recorder through a potential
divider, which decreases this 1-Ov to the voltage
required for full-scale deflexion of the recorder, and,
if the negative terminal of the recorder is connected
through a ten-point stepping switch to a chain of
resistors giving voltage steps each equal to the fullscale-deflexion
voltage, the problem is solved. For
example, if the recorder has a range of lmv, the
potential divider must give a 1000-fold voltage
decrease and the resistor chain must give 1 mv steps.
Circuit. Fig. 1 shows the circuit of the unit as
designed for an auxiliary recorder of lmv fullscale
deflexion. The unit itself is shown to the left
of the broken line; the components shown on the
ด้านขวาของบรรทัดอยู่แล้วเป็นส่วนของ
วงจรของเบคแมน dk2 เครื่องดนตรีและ r2a
-
0-7 0-9 ขาวอ้อยเสียใจเส้นโพเทนซิโอมิเตอร์ - . 06 อาร์เอท 500ks2 ( 0
< ลี่ = 0
-
0 4 บันทึก , r4
O
- 500
offl 0-2 สีเทา ผม _15 45N ( tv5f
รูปที่ 1 วงจรเครื่องขยายขนาดการสูญพันธุ์
หน่วยจะแสดงที่ด้านซ้ายของเส้นแตก ; ส่วนประกอบ
on the right of the line form part of the existing circuit of
the Beckman DK2 spectrophotometer, as set for extinction
measurements. The numbered squares represent the
terminal lugs to which wires are taken from the unit. ' A'
denotes 'absorbance' as shown by the position of the pen
of the Beckman DK2 instrument. Resistors B3 and R4
form the 1000-fold potential divider (more accurately 999-
fold, but the scarcely detectable difference is within the
tolerance of the resistors, and in any case is taken care of
by the initial adjustments).
require no modification. The circuit is shown as it
appears when in use for extinction measurements.
The logarithmic potentiometer that controls the
pen movements under these conditions is not shown.
The chain of resistors on the left is supplied from
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