Time Electronics 1040 Resistance Decade Box - Manual (Page 4)

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1040 Technical Manual 3
2. Operation of the 1040
The 1040 is a compact, robust and accurate decade resistance box designed to meet the
needs of both industry and education. Housed in a robust metal case, the compact
construction makes it easily portable.
Metal film resistors are used to obtain the high stability and low temperature co-efficient.
It is imperative that the switch setting should be unambiguous in order to avoid misreading
the set value. To prevent misreading, the 1040 incorporates a unique colour coding system
to divide the setting into 3 groups corresponding to ohms, kilohms and megohms.
Resistance is simulated by dialling the value required using the thumbwheel switches. This
enables precise setting with a clear unambiguous indication. For example—to simulate
3k83 set the 1k bank to 3, the 100Ω bank to 8 and the 10Ω bank to 3, all the other dials set
to zero.
Connection to the box is via 4mm terminal posts, 4mm plugs or stripped wire connections
can be used.
The red and black terminals connect to the resistance and the grey terminal is connected to
the case for screening purposes.
Special attention has been given to the problem of reliability of operation. A special multiple
gold contact switch arrangement ensures that a back-up contact is always available to take
over should a failure occur.
Note : Remember that all resistance boxes have a residual resistance, i.e. when the dials
are set to zero a small resistance remains. If you are making precision measurements or
recalibrating the instrument, this residual value must be subtracted from all measurements.