Ashcroft® 400 & 700 B Series Pressure Switch Calibration Instructions

Easy to follow calibration instructions for Ashcroft® 400 & 700 B Series Pressure Switches.

JOIN THE ASHCROFT COMMUNITY
Facebook:   / ashcroftinc  
Twitter:   / ashcroft_inc  
LinkedIn:   / 72644  
YouTube:    / ashcroftinc  

VIDEO TRANSCRIPT:
Welcome. This video will detail calibration instructions for the B-Series Pressure Switches. We’re going to calibrate a B424 Switch.
We have three wires connected to the microswitch. The white wire is connected to the common contact, the blue wire in the center is connected to the normally open contact, and the red wire is connected to the normally closed contact. This will allow our lightbox to operate when we open and close the switch. The B-Series switch is a single set point switch with a center adjustment nut that’s in there. The nut is actually marked with the directions to turn it in either direction. And there is also a feature of a set point locking screw. So before you attempt an adjustment, you need to loosen the set point locking screw, which is right here, with a couple of turns.
We are now ready to test the switch. The first thing we do is we exercise the switch. We take it from 0 psi to the full range, which is 100 psi.
Next, we’re going to set this switch on an increasing set point and we’re going to set this for 80 psi increasing.
The switch is not turned on at this point. Since it is not turned on, we’re going to turn the nut counter-clockwise to decrease the force on the spring and cause the switch to turn on.
The switch just turned on. Now what we’re going to do is lower the pressure back to 0 and come up slowly to see exactly the turn-on point of the switch. We will bring the pressure up close to where it’s going to turn on, and then fine-tune it.
And it turned on just a little bit too soon, so we’re going to need to make a slight adjustment and correct that. So the easiest thing to do would be to make a small adjustment on the adjustment nut, approximately a quarter of a turn, and then we’ll take it back down to 0.
And go back up.
We are right on 80, but we have not turned it. So we’re going to do a turn back just slightly for adjustment. We should be fairly close now. We’ll go back down to 0. And go up, and repeat the measurement point.
Looks like it’s right on 80 now. Now we can measure the deadband. So we are going to just turn the pressure back until the switch turns off.
Looks like it’s 77.5, so it would be 2.5 psi deadband for this switch. So now we would just repeat this measurement to verify the set point.
---
We are going to calibrate a B724 Switch. Like the B400, there is a single adjustment nut in the center of the switch. There is not a locking setpoint screw on this one. There is a rod, which helps hold it in place that is just on the nut. The first part of our calibration is we are going to exercise the switch and then we are going to set this switch for a 20psi decreasing setpoint. For the decreasing setpoint, we always go full scale and come back down. So, we are going to take it to 100psi and then down to our setpoint of 20.
Now, we are going to bring it down to 20. It’s a little over 20, so we will do one slight adjustment, which would bring it back it out just a little bit more.
We will test it again by taking it up to the full range.
[00:05:18] There it goes. It’s right at 20. And from here we would check our deadband by increasing the pressure to see where it turns back on again.
And that looks like about 3.5psi deadband; so 23.5 it turned back on.
We would repeat this, taking it to full scale and down to 20 and back up again 3 times to verify repeatability of the switch.
Thank you for watching. Please visit www.Ashcroft.com for more detailed product information. Or subscribe to our YouTube channel for additional demonstrations.