[time-nuts] Re: Datum PRS-50 monitoring software

[Jim Harman]

If your RS-232 dongle has a separate USB cable, make sure the cable is
fully functional and is not a charge only type. This has tripped me up a
couple of times. You should hear the Windows "bing bong" sound when the
dongle is plugged in, and if you connect the TXD and RXD lines and type
something into a serial monitor on the PC you should see it echoed back.

Another common issue with RS-232 connections is the need for a null modem
that swaps the RXD and TXD lines, pins 2 and 3 on either the 9 pin or 25
pin connectors. If you measure the voltage on these pins, the TXD will idle
at about -5 V and the RXD will be near zero. The TXD on one side must be
connected to the RXD on the other.

And of course the baud rates must match.

On Wed, Dec 28, 2022 at 11:44 PM va2hdd--- via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hello to all members.
>
> I recently purchased a Datum PRS-50 that looks like a spare unit, almost
> mint. When I connect it to a lab PS set to 48 volts the current
> stabilise at around 0,5 Amp, the LED's light up according to the
> sequence described in the manual and the unit eventually goes into
> cesium lock with a very nice 5.000000046 MHz output.
> The cesium lock LED stays on for a while, then the unit goes in alarm,
> then back to cesium lock, then alarm ...  I suspect that the ion pump
> need to improve the vacuum in the CS tube.  I tried to use the "monitor
> 3" Windows software to watch ion pump current but I was never able to
> get it communicating both with front or rear connector, I installed the
> software on a Windows 10 PC and used a USB to RS-232 dongle.  I tried
> three different chipset USB-232 adapters with the same result.  My unit
> does not have the "TL1" option, and on page 2.2 of the manual in table
> 2.3-1 it is mentioned that without the TL1 interface I should be using
> the DOS version (Monitor.EXE).  I tried to find it but had no luck.
>
> Best regards,
>
> Claude VA2 HDD
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-- 

--Jim Harman