N8754A- Power supply does not output the configured value at the first measurement

[madhu27]

Hi There,

I am new dealing with instruments. I am using Power Supply N8754a. I downloaded the instrument driver from the below webpage.

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=818EC3FFD3E92482E04400144FB7D2...

It has two examples. I just modified both the examples by removing the while loop and making it to run once. (I made this change since I don't want any human intervention to stop the while loop.) They work fine when I set reset as false. But on reset (default in those examples), say, if I want to set to 5V, the power supply output is set as 0.01V (most of the times), or some value between 0 to 4 (sometimes), and rarely 5V. But when I read the power supply output for the second time, it is set as 5V. (By second time, i mean placing the measure API twice). I tried giving delay also. But it is not the case. It seems like the value is gradually increasing to reach 5V. But how much ever i increase the value, i am getting the required value at the second measurement. Not sure whether this is the default behaviour or I am missing out something.

1. Initialize>>Configure>> Enable Output>> Measure  ->Works

2. Initialize>>Reset>>Configure>> Enable Output>> Measure -> Doesnot work

3. Initialize>>Reset>>Configure>> Enable Output>> Measure>> Measure ->Works

Any help is appreciated!

Thanks,

Madhumithra

[Dennis_Knutson]

How long are you waiting after resetting the instrument?

[madhu27]

I tried waiting for a maximum of 2 minutes after reset.

[nyc_(is_out_of_here)]

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@madhu27 wrote:

Hi There,

I am new dealing with instruments. I am using Power Supply N8754a. I downloaded the instrument driver from the below webpage.

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=818EC3FFD3E92482E04400144FB7D2...

It has two examples. I just modified both the examples by removing the while loop and making it to run once. (I made this change since I don't want any human intervention to stop the while loop.) They work fine when I set reset as false. But on reset (default in those examples), say, if I want to set to 5V, the power supply output is set as 0.01V (most of the times), or some value between 0 to 4 (sometimes), and rarely 5V. But when I read the power supply output for the second time, it is set as 5V. (By second time, i mean placing the measure API twice). I tried giving delay also. But it is not the case. It seems like the value is gradually increasing to reach 5V. But how much ever i increase the value, i am getting the required value at the second measurement. Not sure whether this is the default behaviour or I am missing out something.

1. Initialize>>Configure>> Enable Output>> Measure  ->Works

2. Initialize>>Reset>>Configure>> Enable Output>> Measure -> Doesnot work

3. Initialize>>Reset>>Configure>> Enable Output>> Measure>> Measure ->Works

Any help is appreciated!

Thanks,

Madhumithra

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What does the programmer's manual for the instrument say?

[madhu27]

I didnot find anything mentioned specifically related to this. Since the example program from NI had the while loop, i doubt whether this shall be the default behaviour.

[madhu27 · Accepted solution]

Hi all,

Initially, I had tried giving the delay after reset, which didnot work. Now, i am able to get it work by giving the delay of 1.5s after enabling the output. 

Thanks for all your reply!

Madhumithra

[crossrulz]

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@madhu27 wrote:

Hi all,

Initially, I had tried giving the delay after reset, which didnot work. Now, i am able to get it work by giving the delay of 1.5s after enabling the output. 

Thanks for all your reply!

Madhumithra

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That makes sense.  It takes time for power supplies (especially high current power supplies) to charge up their capacitor bank and get up to the set voltage.  I have seen some take as long as 3 seconds to settle.