20.
Resistance Ranges
- 2 ohm, 20 ohm, 200
ohm and 200K ohm - silicone boots provide
water-resistance (small LED indicates the
selected range).
21.
Power “On or OFF/Charging Switch”
22.
Beveled Display Hood
and Super Bright
LED Display ( five times brighter than
bright yellow, red or green LEDs).
23.
Padlock Hole
(i.e. security) while stored
or during transit.
D-3. Fuseholder and Charging System
Fuseholder
The fuseholder is mounted on the front panel
and contains a 2 amp in-line fuse (see item 7
of the 630ES Front Panel Diagram.). This
fuse is designed to protect the internal
battery pack from excessive charging
currents. Replace blown fuses with the
same type and rating only!
The Charging System
The slimline AC to DC battery charger with
connector is a notched connector that mates
with only two of the 8 pin/socket mating
points on the main panel mount connector
(see Main Connector J1 Section E6 for
pinout definitions). The connection is made
on the 630ES front panel (see item 4 of the
630ES Front Panel Diagram shown earlier).
Again the
Single Access
Multipurpose
Notched
Main Connector
is for
either
test
lead hookup
or
connection to the battery
charger but not both at the same time.
With
only one connector to the outside world
, it
is physically
impossible
to do both at the
same time (charge and measure). The power
switch (item #21) must also be in the
“Off/Charging” mode while the battery
charger is connected in order to recharge the
batteries. The charging requirements
supplied to the internal battery pack are
internally stepped down from the 9VDC
@1.1A supplied by the charger. The correct
charging voltage is supplied by the adapter
included with the instrument. Additional
AC/DC Battery Chargers are available as
Option "630DC". Typically an
overnight
charge (16 hours) will provide about an 6 to
8 hour continuous powered up life for the
630ES. The 630ES have an internal
ovenized voltage reference the draws a
considerable amount of battery power when
first turned on. If you know you will be
using the 630ES again in 10 to 15 minutes,
you actually conserve battery power by not
turning it off.
D-4. 4-Wire Resistance Measurement
The four-terminal configuration of the
630ES eliminates errors normally caused by
in series test lead resistance and contact
resistances. In many applications the contact
resistance and can exceed the value of the
test resistance by several orders of
magnitude. The 630ES overcomes this
potential error source by providing two
terminals of constant current and an
additional two terminals for high impedance
voltage measurement. The result is a fast,
accurate resistance measurement of the test
resistance, independent of the resistance of
the current carrying leads.
Figure D-1
(below) illustrates how the 4-
wire principle is used to eliminate lead, wire
and contact resistances as potential error
sources. The internal current source
inherently overcomes all series resistance
(within compliance voltage limits) and
delivers a precise constant current. The
internal high-impedance DVM senses the
voltage drop across the test resistance.
There is negligible contact and lead
resistance error created by the voltage
measurement because the high input
impedance of the DVM limits current flow
in the voltage leads.
