REPORT
You can measure l / 1 0 0 t h of a millivolt with this superior quality potentiometer recorder. Unit is extremely accurate (Vfe% of span), and fast (V2 second balance time). Step selection of ranges up to 10 V is provided by attenuator on front panel. Standard features include a floating input with separate chassis ground . . . 5" chart width . . . hum suppressor . . . chopper stabilization . . . changeable chart speeds. Write for Bulletin. 10 MV fixed span 10 MV to 100 V 1 MV full scale
$320.00 $395.00 $535.00
Model JY-100 Model JY-110 Model JY-120
Manufacturers of Precision Recording
Instruments
6 3 8 West 1 7 t h St., Costa Mesa, Calif. Circle No. 130 on Readers' Service Card
TOOLS FOR A BREAKTHROUGH!$
M
ing feature, a meter having a fullscale deflection (f.s.d.) of 200 μ,Ά. would have to be used, and the signal of interest would have to be read as the small difference be tween two large deflections. With the current-bucking arrangement, a higher sensitivity meter can be used to display the lO-^a. signal directly. The "zero adjust" sliding contact permits the grid potential to be varied when the flame is burning, in order to adjust the read-out meter to zero deflection when no sample is being introduced into the flame. Two-Stage Electrometer Ampli fier. If a higher gain is required than is available with the singlestage electrometer just described, its output may be direct-coupled to a second stage of amplification, as shown in the circuit of Figure 3 [Hansen, R. E., Buell, M. V., ANAL.
31, 878 (1959)]. In this case, the transducer is a multiplier photo tube, the anode of which is connected to the top of the grid input (or, dropping) resistor, Β.Λ. Photoelectrons reaching the anode flow down through i?i and create an 772 drop across it, making the grid of the CK5889 electrometer tube more negative, the greater the photocurrent. The more negative this grid is, the smaller is the tube current flowing through the elec trometer and the smaller is the 772 drop through the plate load resistor, 72i4- A decrease in this IR drop is equivalent to an increase in the po tential at the plate of the electrom eter tube. This plate is directly coupled, through Ε is, to the grid of the 6AU6 tube. Hence, a negativeCHEM.
TO
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Figure 7. Differential cathode follower circuit, used to couple a sig nal from a high internal impedance source to a low input impedance read out device Circle No. 33 on Readers' Service Card
34 A
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RECORDER
ANALYTICAL CHEMISTRY
