Lake Shore Cryotronics 420 Instructions

Instructions, Gaussmeter, Cable, and
HALLCAL.EXE
CAUTION: This Hall sensor is sensitive to electrostatic discharge (ESD). Use ESD precautionary
procedures when handling, or making mechanical or electrical connections to this device in order to
avoid performance degradation or loss of functionality.
1.0 GENERAL
This document provides operation instructions for operating a Hall sensor with a Lake Shore 420, 421,
450, or 460 gaussmeter. Using a Hall sensor with a Lake Shore gaussmeter is described in Paragraph
1.1. MCBL-6 and MCBL-20 programmable cables details are provided in Paragraph 1.2. Finally, setup
and operation of the Hallcal.exe software is described in Paragraph 1.3.
Instructions in this chapter are intended for the low impedance "bulk" Hall sensors. The instructions do not
apply to HGT-2100, HGT-2010, and HGA-2010 (which are intended for use with the Model 410
gaussmeter). The impedance and control current requirements of these three Hall sensors are not
compatible with the Lake Shore gaussmeters that use the MCBL cables.
1.1 USING A HALL SENSOR WITH A LAKE SHORE GAUSSMETER
To hook up a Hall sensor, you must use a Lake Shore MCBL-6 or MCBL-20 cable assembly (Paragraph
1.2). The MCBL-6 cable is 2 m (6.5 ft) long with a DA-15 connector on one end and four leads on the
other. The MCBL-20 cable is 6 m (20 ft) long. The Hall sensor is a 4-lead device. The 4 leads are labeled
+Ic (Red), –Ic (Black or Green), +VH (Blue), and –VH (Yellow), corresponding to the 4 leads on all the Hall
sensors.
The typical Lake Shore 421, 450, or 460 gaussmeter has an input impedance of 420 Ω. Therefore, the
actual sensitivity at the gaussmeter input will be less than the value given with the Hall sensor due to drop
in the leads and cable. This fact is important because a sensitivity value is supposed to be loaded into the
cable PROM to set calibration. We recommend that the customer always check accuracy against a
reference field rather than use the sensitivity value sent with the bare Hall generator. Because Lake Shore
has no control of the conditions beyond the cable, the customer must accept responsibility for accuracy
and compatibility.
Finally, Manganin wire is not usually acceptable for gaussmeter connections. The resistance of Manganin
wire is often too high. Hall generators are normally connected using twisted pairs of copper wire such as
34 gauge, Teflon insulated. There are two reasons for this:
1. The gaussmeter current source is limited in compliance voltage. The gaussmeter should not drive
a load (Hall sensor, wires in cryostat, and probe cable) greater than 50 Ω. In fact, for best
performance, the load should be less than 30 Ω.
2. Because the typical Lake Shore gaussmeter input impedance is 420 Ω, there is a voltage drop due to
lead resistance in series with the gaussmeter input. The Lake Shore Hall sensor sensitivity given on
the data sheet is basically with no lead resistance. See Figure 1-1.
The gaussmeter needs input sensitivity
between 0.5 to 1.5 mV/kG (HST) or
5.0 and 15 mV/kG (HSE) at its input
Gaussmeter
Input
Sensitivity at Gaussmeter input is
reduced by the lead/input voltage divider
Lake Shore Cryotronics, 575 McCorkle Blvd. Westerville, OH 43082
Phone (614) 891-2243 – Fax (614) 891-1362 –
R
cable
420 
R
cable
R = Lake Shore Model
cable
MCBL Cable Assembly
Figure 1-1. Typical Hall Sensor Input Impedance
sales@lakeshore.com
R Hall Generator
cust
Open Circuit
Sensitivity
V
H
R
cust
R = Customer
cust
Supplied Leads
www.lakeshore.com
–
service@lakeshore.com
Impedance2.cvx