Boston Electronics Corporation, 91 Boylston Street, Brookline MA 02445
(800)347-5445 or (617)566-3821 * fax (617)731-0935 * boselec@boselec.com * www.boselec.com
Bartles Industrial Estate, North Street, Redruth, Cornwall TR15 1HR
Tel. (01209) 314608 E-mail: scitec@scitec.uk.com
Fax. (01209) 314609 Web: http://www.scitec.uk.com
2 OPERATION
After first ensuring that the current voltage selection is appropriate to your power supply, the
power can be connected to the rear of the unit. The power supply switch (16)
1
is mounted on
the front panel and causes the power on indicator to light (15).
Please note that the instrument has a number of circuits within it that require time to settle on
power up. This can cause the output meter to jump to full scale for a short time on power up.
This is most noticeable if the time constant control (3) is set to a high value (above 1S). To
speed up the settling process turn the time constant control (3) to 1S or below.
If there is no reference signal connected to the unit then the offset nulling circuitry within the
unit does not operate and hence an offset may be seen on the output. This is normal and will be
removed when a reference signal is applied.
It is safe to apply signals to the unit while the lock-in is switched off, though this is not
recommended for any length of time. However, the input impedance of the signal input and
reference input with unit switched off may drop producing an unacceptable load on the sources
of these signals. It is hence recommended that the unit is switched on whenever input signals
are applied to it.
Care should be made that the reference signal does not affect the input signal. The reference
signal is commonly many factors larger than the signal to be measured and it is therefore
relatively easy for the reference signal to be picked up on input signal cable. For this reason
keep the cabling for the input signal as far away as possible from the cabling for the reference
signal. Careful screening helps but it is still possible for the input cable to pick up the reference
signal if significant lengths are put into close contact.
1
The numbers in brackets refer to the numbers used in Figure 18 at the back of this manual.
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