Analogue output is either
External Inhibit. Opto-isolated input, triggered by 5 - 20V or 3 - 15mA at terminals.
Serial portTwo independent control signals are provided by no-volt relay contacts, rated at 24V 0.5A ac or dc. Alarm signal provided by an open collector output, 50mA maximum. Set points and channel assignment via the front panel controls.
Connector: DB9-M connector on the back panel.Provides a second standard 7 pin probe input socket on the back panel, and a second probe cable. Allows two helium and/or nitrogen probes to be connected at the same time.
Provides the facility to connect one or two probes via one Lemo connector instead of one (or two) standard 7 pin connector(s). This option is particularly suited for wire ended helium probes installed within a cryostat, and where the customer provides the external wiring. The mating connector is supplied, but no probe cables.
Connector: 1B series, 8 pin Lemo.For units with either the 2 or L options, the Z option provides a second analogue output corresponding to the reading from the second probe. When this option is selected, the External Inhibit is not available, as the second output is fed from the second pair of pins in the shared MOLEX connector. Both analogue outputs are of the same type, that is A, V or T.
From autumn 2002, the probe range which the HDI unit has been calibrated for will be explicitly stated in the product part number
In 2001, a second probe range, G, was introduced, and this code letter was added to the product part number. The original probe range, S, will now also be added to the product part number, although this will not apply to units supplied before autumn 2002. The code letter will be put after the analogue output code letter. Examples are given in the Helium probe details page.
The probe range only affects the calibration of the HDI unit. Instructions are given in the product manual to convert the unit from one probe range to the other. This only requires a few test components and about five minutes of time.
HDI units have been supplied set up for non-Twickenham probes. Such units will continue to be supplied with the special set-up described as a special option.
The probe range S should not be confused with the former option of serial port, (now a standard feature), which, unfortunately, used the same letter. However, the option for a serial port was withdrawn some years ago, so there should not be any confusion of an old unit with the letter S in the product part number.
This matter is discussed more fully in the pages concerning helium probes.
These options specify the removal of an item normally supplied, and the substitution, where appropriate of an alternative.
Where the HDI is to be Rack or Panel mounted only, and that the base panel with feet attached will not ever be required, specifying the R supply option will mean that the HDI is supplied with two blank panels, and no panel with feet.
In some cases, the system already has all the wiring extant, and that only
the suitable connector is required for installation to the HDI, rather
than the standard 4m probe cable. (Likewise with the Lemo connector
probe input option). These are:
P The standard probe cable is replaced by the 7 pin male connector and hood.N Neither probe cable or 7 pin connector are supplied for the probe input connector.
If the 2 option is also required for the system:
2P One probe cable and one 7 pin male connector and hood.
2P2 Two 7 pin male connectors and hoods; no probe cables.