She has launched broadcaster UTV's high definition television service in Belfast and will meet business leaders during a Hillsborough dinner. Guests at the UTV reception said she was interested in the science of broadcasting.
Northern Ireland Secretary Owen Paterson welcomed her at the airport and said: "She is into the new technology, she is tremendous the way she works the new technology."
She was met by First Minister Peter Robinson and Belfast Lord Mayor Pat Convery as well as senior UTV executives.
The Duke of Edinburgh accompanied the monarch.
She met UTV weatherman Frank Mitchell in the studio, who explained the system. He said: "I checked before meeting her with some of the technical people and I was impressed that she asked technical questions about the science of how the technology worked."
He showed her a variety of backgrounds for presenters including the world-famous Giant's Causeway and Buckingham Palace.
After seeing that she remarked, "you could take me anywhere in the world".
Mr Mitchell said afterwards: "It was a very casual, witty comment from a woman you don't expect to be witty. I was impressed by how friendly she was."
As patron of Action for Children, the monarch will be guest of honour at a Hillsborough Castle reception to celebrate the charity's 10th anniversary in the Northern Ireland region.