Hello Everyone,
I am trying to connect the ISCO samplers with the CR800. The sampling part is working fine.The bottle count of the sampler is fed back to the logger through the pulse channel by a 12V pulse. The no of 12V pulse recorded is proportional to the bottle no. I use the pulse count instruction with the High frequency option and count,It's not counting any pulse. When i measure the pulse channel without any wires connected, I measure 4.96V in them. From the manual the high frequency is measured when the rise is above 0.9V ( from top of my head) and the fall is 2.4V. Its constantly measuring 4.96 V so no pulse is recorded. I have replicated the same setup with another logger no samplers connected still it reads 4.96V.
Has anyone seen this type of issue before. either it will be a silly mistake i am doing or something wrong with the logger.
Your time and help would be much appreciated.
CR1000 manual, Section 4.5.1.1
"When a pulse channel is configured for high-frequency pulse, an internal 100 kΩ pull-up resistor to 5 Vdc on the P1 or P2 input is automatically employed. This pull-up resistor accommodates open-collector/open-drain output devices for high-frequency input."
That is why you are measuring ~5V on the terminal.
What you are describing is a current source, not a current sink. Can you reconfigure the port of the ISCO to be a current sink?
If not, I suggest using a C port instead of a P port.
Just to follow on from Sam, the 100k is there to allow easy connection of most open collector type sensors, but it does not preclude the more common pulse output sensor which drive the input to the logger, as long as the sensor can take the input down below 0.9 V and up above 2.2V it will work.
The fact there is a 100k resistor pulling to 5V should not affect any sensor which claims to drive its output because the 100k is such a high resistance.
CS supports use of at least one model of ISCO sampler and there is a manual for the cable and connection:
http://www.campbellsci.com/documents/manuals/10164.pdf
That shows using a 20k resistor in series with the output line. This is there I believe to limit current output from the sensor if connecting to a control port on the logger.
If connecting to a pulse count port this resistor is not needed and such a high resistance should probably not be used as it could make the logger more sensitive to noise or even prevent operation if there are significant ground differences.
For what it's worth, I've gotten the bottle count to work on CR2xx dataloggers using the P_LL port using the PConfig option of 1 (Low Level). This is with the ISCO 3700 series of samplers. I've used the cables that Andrew mentioned above and cables that we've made ourselves with amphenol connectors. If I recall correctly, we installed a 20k resistor. As Andrew mentioned above, it may work better without the resistor. I don't remember.
The pulse signal should be Pin D (brown cable on above mentioned 10164 cable) on the ISCO Flowmeter connector and ground on Pin B (purple cable).
I'm not sure what my CR2xx setup would correspond to on the CR800.
Hello Everyone,
Thanks for your feedback and help. I got it working as Sam suggested. I connected the ISCO sampler 3700 (Pin D) through the control port, it was working fine.
Have a nice day
Regards
Jeeva Prakasan